Sunday, August 28, 2011

An Observation upon the IBGP and EBGP Route Removal

Scenario #1

Scenario #2

In scenarios 1 and 2, the IBGP- and EBGP-learnt route 192.168.2.0/24 is removed from the IP routing table of RT1 upon the failure of the RT1-RT2 link.

Scenario #1:
RT1#sh ip route

Gateway of last resort is not set

      12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        12.12.12.0/30 is directly connected, FastEthernet1/0
L        12.12.12.1/32 is directly connected, FastEthernet1/0
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, FastEthernet0/0
L        192.168.1.1/32 is directly connected, FastEthernet0/0
B     192.168.2.0/24 [200/0] via 12.12.12.2, 00:00:16
RT1#
RT1#sh ip bgp
BGP table version is 3, local router ID is 192.168.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.1.0      0.0.0.0                  0         32768 i
*>i192.168.2.0      12.12.12.2               0    100      0 i
RT1#
RT1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
RT1(config)#int fa1/0
RT1(config-if)#shut
RT1(config-if)#end
RT1#
RT1#sh ip bgp
BGP table version is 4, local router ID is 192.168.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.1.0      0.0.0.0                  0         32768 i
* i192.168.2.0      12.12.12.2               0    100      0 i
RT1#
RT1#sh ip route

Gateway of last resort is not set

      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, FastEthernet0/0
L        192.168.1.1/32 is directly connected, FastEthernet0/0
RT1#

Scenario #2:
RT1#sh ip route

Gateway of last resort is not set

      12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        12.12.12.0/30 is directly connected, FastEthernet1/0
L        12.12.12.1/32 is directly connected, FastEthernet1/0
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, FastEthernet0/0
L        192.168.1.1/32 is directly connected, FastEthernet0/0
B     192.168.2.0/24 [20/0] via 12.12.12.2, 00:00:18
RT1#
RT1#sh ip bgp
BGP table version is 3, local router ID is 192.168.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.1.0      0.0.0.0                  0         32768 i
*> 192.168.2.0      12.12.12.2               0             0 200 i
RT1#
RT1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
RT1(config)#int fa1/0
RT1(config-if)#shut
RT1(config-if)#end
RT1#
RT1#sh ip bgp
BGP table version is 4, local router ID is 192.168.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.1.0      0.0.0.0                  0         32768 i
RT1#
RT1#sh ip route

Gateway of last resort is not set

      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, FastEthernet0/0
L        192.168.1.1/32 is directly connected, FastEthernet0/0
RT1#


The objective of this article is to document the observation upon the removal of an IBGP route when the IBGP neighbor address (which is also the BGP Next Hop) is within the range of an IBGP-learnt supernet route.

Scenario #3
Scenario #3:
RT1#sh ver
Cisco IOS Software, 7200 Software (C7200-SPSERVICESK9-M), Version 12.2(33)SRE4, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2011 by Cisco Systems, Inc.
Compiled Mon 30-May-11 03:09 by prod_rel_team

ROM: ROMMON Emulation Microcode

RT1 uptime is 1 minute
System returned to ROM by unknown reload cause - suspect boot_data[BOOT_COUNT] 0x0, BOOT_COUNT 0, BOOTDATA 19
System image file is "tftp://255.255.255.255/unknown"


This product contains cryptographic features and is subject to United
States and local country laws governing import, export, transfer and
use. Delivery of Cisco cryptographic products does not imply
third-party authority to import, export, distribute or use encryption.
Importers, exporters, distributors and users are responsible for
compliance with U.S. and local country laws. By using this product you
agree to comply with applicable laws and regulations. If you are unable
to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:
http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to
export@cisco.com.

Cisco 7206VXR (NPE400) processor (revision A) with 114688K/16384K bytes of memory.
Processor board ID 4294967295
R7000 CPU at 150MHz, Implementation 39, Rev 2.1, 256KB L2 Cache
6 slot VXR midplane, Version 2.1

Last reset from power-on

PCI bus mb0_mb1 (Slots 0, 1, 3 and 5) has a capacity of 600 bandwidth points.
Current configuration on bus mb0_mb1 has a total of 400 bandwidth points.
This configuration is within the PCI bus capacity and is supported.

PCI bus mb2 (Slots 2, 4, 6) has a capacity of 600 bandwidth points.
Current configuration on bus mb2 has a total of 0 bandwidth points
This configuration is within the PCI bus capacity and is supported.

Please refer to the following document "Cisco 7200 Series Port Adaptor
Hardware Configuration Guidelines" on Cisco.com 
for c7200 bandwidth points oversubscription and usage guidelines.


2 FastEthernet interfaces
125K bytes of NVRAM.

65536K bytes of ATA PCMCIA card at slot 0 (Sector size 512 bytes).
8192K bytes of Flash internal SIMM (Sector size 256K).
Configuration register is 0x2102

RT1#
RT1#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP
       + - replicated route, % - next hop override

Gateway of last resort is not set

      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, FastEthernet0/0
L        192.168.1.1/32 is directly connected, FastEthernet0/0
      192.168.2.0/24 is variably subnetted, 3 subnets, 3 masks
B        192.168.2.0/24 [200/0] via 192.168.2.2, 00:00:26
C        192.168.2.0/30 is directly connected, FastEthernet1/0
L        192.168.2.1/32 is directly connected, FastEthernet1/0
RT1#
RT1#sh ip bgp summary
BGP router identifier 192.168.2.1, local AS number 100
BGP table version is 3, main routing table version 3
2 network entries using 256 bytes of memory
2 path entries using 104 bytes of memory
2/2 BGP path/bestpath attribute entries using 248 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 608 total bytes of memory
BGP activity 2/0 prefixes, 2/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.2.2     4          100       5       5        3    0    0 00:01:15        1
RT1#
RT1#sh ip bgp
BGP table version is 3, local router ID is 192.168.2.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.1.0      0.0.0.0                  0         32768 i
*>i192.168.2.0      192.168.2.2              0    100      0 i
RT1#
RT1#sh ip bgp neighbors 192.168.2.2
BGP neighbor is 192.168.2.2,  remote AS 100, internal link
  BGP version 4, remote router ID 192.168.2.254
  BGP state = Established, up for 00:01:15
  Last read 00:00:25, last write 00:00:26, hold time is 180, keepalive interval is 60 seconds
  Neighbor sessions:
    1 active, is multisession capable
  Neighbor capabilities:
    Route refresh: advertised and received(new)
    Four-octets ASN Capability: advertised and received
    Address family IPv4 Unicast: advertised and received
    Multisession Capability: advertised and received
  Message statistics, state Established:
    InQ depth is 0
    OutQ depth is 0

                         Sent       Rcvd
    Opens:                  1          1
    Notifications:          0          0
    Updates:                2          2
    Keepalives:             2          2
    Route Refresh:          0          0
    Total:                  5          5
  Default minimum time between advertisement runs is 0 seconds

 For address family: IPv4 Unicast
  Session: 192.168.2.2 session 1
  BGP table version 3, neighbor version 3/0
  Output queue size : 0
  Index 1
  1 update-group member
                                 Sent       Rcvd
  Prefix activity:               ----       ----
    Prefixes Current:               1          1 (Consumes 52 bytes)
    Prefixes Total:                 1          1
    Implicit Withdraw:              0          0
    Explicit Withdraw:              0          0
    Used as bestpath:             n/a          1
    Used as multipath:            n/a          0

                                   Outbound    Inbound
  Local Policy Denied Prefixes:    --------    -------
    Bestpath from this peer:              1        n/a
    Total:                                1          0
  Number of NLRIs in the update sent: max 1, min 0
  Last detected as dynamic slow peer: never
  Dynamic slow peer recovered: never

  Address tracking is enabled, the RIB does have a route to 192.168.2.2
  Connections established 1; dropped 0
  Last reset never
  Transport(tcp) path-mtu-discovery is enabled
  Graceful-Restart is disabled
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled
Mininum incoming TTL 0, Outgoing TTL 255
Local host: 192.168.2.1, Local port: 15732
Foreign host: 192.168.2.2, Foreign port: 179
Connection tableid (VRF): 0

Enqueued packets for retransmit: 0, input: 0  mis-ordered: 0 (0 bytes)

Event Timers (current time is 0x17F9C):
Timer          Starts    Wakeups            Next
Retrans             4          0             0x0
TimeWait            0          0             0x0
AckHold             3          2             0x0
SendWnd             0          0             0x0
KeepAlive           0          0             0x0
GiveUp              0          0             0x0
PmtuAger            1          0         0x9810C
DeadWait            0          0             0x0
Linger              0          0             0x0

iss: 3426928912  snduna: 3426929087  sndnxt: 3426929087     sndwnd:  16210
irs: 1337499386  rcvnxt: 1337499561  rcvwnd:      16210  delrcvwnd:    174

SRTT: 124 ms, RTTO: 1405 ms, RTV: 1281 ms, KRTT: 0 ms
minRTT: 108 ms, maxRTT: 300 ms, ACK hold: 200 ms
Status Flags: none
Option Flags: higher precendence, nagle, path mtu capable

Datagrams (max data segment is 1460 bytes):
Rcvd: 6 (out of order: 0), with data: 4, total data bytes: 174
Sent: 8 (retransmit: 0 fastretransmit: 0),with data: 4, total data bytes: 174

RT1#
RT1#ping 192.168.2.254 source 192.168.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.2.254, timeout is 2 seconds:
Packet sent with a source address of 192.168.1.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/26/52 ms
RT1#
RT1#sh ip int brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        192.168.1.1     YES NVRAM  up                    up
FastEthernet1/0        192.168.2.1     YES NVRAM  up                    up
RT1#
RT1#debug ip bgp
BGP debugging is on for address family: IPv4 Unicast
RT1#
RT1#debug ip routing
IP routing debugging is on
RT1#
RT1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
RT1(config)#int fa1/0
RT1(config-if)#shut
RT1(config-if)#end
RT1#
10:20:45: is_up: FastEthernet1/0 0 state: 6 sub state: 1 line: 1
10:20:45: RT: interface FastEthernet1/0 removed from routing table
10:20:45: RT: del 192.168.2.0 via 0.0.0.0, connected metric [0/0]
10:20:45: RT: delete subnet route to 192.168.2.0/30
10:20:45: RT: delete route to 192.168.2.1 via 0.0.0.0, FastEthernet1/0
10:20:45: RT: no routes to 192.168.2.1, flushing
10:20:47: %LINK-5-CHANGED: Interface FastEthernet1/0, changed state to administratively down
10:20:47: is_up: FastEthernet1/0 0 state: 6 sub state: 1 line: 1
10:20:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/0, changed state to down
10:20:48: is_up: FastEthernet1/0 0 state: 6 sub state: 1 line: 1
RT1#
RT1#sh ip bgp summary
BGP router identifier 192.168.2.1, local AS number 100
BGP table version is 3, main routing table version 3
2 network entries using 256 bytes of memory
2 path entries using 104 bytes of memory
2/2 BGP path/bestpath attribute entries using 248 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 608 total bytes of memory
BGP activity 2/0 prefixes, 2/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.2.2     4          100       5       6        3    0    0 00:01:40        1
RT1#
RT1#sh ip bgp
BGP table version is 3, local router ID is 192.168.2.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.1.0      0.0.0.0                  0         32768 i
*>i192.168.2.0      192.168.2.2              0    100      0 i
RT1#
RT1#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP
       + - replicated route, % - next hop override

Gateway of last resort is not set

      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, FastEthernet0/0
L        192.168.1.1/32 is directly connected, FastEthernet0/0
B     192.168.2.0/24 [200/0] via 192.168.2.2, 00:00:51
RT1#
RT1#sh ip bgp neighbors 192.168.2.2
BGP neighbor is 192.168.2.2,  remote AS 100, internal link
  BGP version 4, remote router ID 192.168.2.254
  BGP state = Established, up for 00:01:41
  Last read 00:00:51, last write 00:00:00, hold time is 180, keepalive interval is 60 seconds
  Neighbor sessions:
    1 active, is multisession capable
    Session: 192.168.2.2
      Topology IPv4 Unicast
  Neighbor capabilities:
    Route refresh: advertised and received(new)
    Four-octets ASN Capability: advertised and received
    Address family IPv4 Unicast: advertised and received
    Multisession Capability: advertised and received
  Message statistics, state Established:
    InQ depth is 0
    OutQ depth is 0

                         Sent       Rcvd
    Opens:                  1          1
    Notifications:          0          0
    Updates:                2          2
    Keepalives:             3          2
    Route Refresh:          0          0
    Total:                  6          5
  Default minimum time between advertisement runs is 0 seconds

 For address family: IPv4 Unicast
  Session: 192.168.2.2 session 1
  BGP table version 3, neighbor version 3/0
  Output queue size : 0
  Index 1
  1 update-group member
                                 Sent       Rcvd
  Prefix activity:               ----       ----
    Prefixes Current:               1          1 (Consumes 52 bytes)
    Prefixes Total:                 1          1
    Implicit Withdraw:              0          0
    Explicit Withdraw:              0          0
    Used as bestpath:             n/a          1
    Used as multipath:            n/a          0

                                   Outbound    Inbound
  Local Policy Denied Prefixes:    --------    -------
    Bestpath from this peer:              1        n/a
    Total:                                1          0
  Number of NLRIs in the update sent: max 1, min 0
  Last detected as dynamic slow peer: never
  Dynamic slow peer recovered: never

  Address tracking is enabled, the RIB does not have a route to 192.168.2.2
  Connections established 1; dropped 0
  Last reset never
  Transport(tcp) path-mtu-discovery is enabled
  Graceful-Restart is disabled
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled
Mininum incoming TTL 0, Outgoing TTL 255
Local host: 192.168.2.1, Local port: 15732
Foreign host: 192.168.2.2, Foreign port: 179
Connection tableid (VRF): 0

Enqueued packets for retransmit: 1, input: 0  mis-ordered: 0 (0 bytes)

Event Timers (current time is 0x1E470):
Timer          Starts    Wakeups            Next
Retrans             5          0         0x1E7A5
TimeWait            0          0             0x0
AckHold             3          2             0x0
SendWnd             0          0             0x0
KeepAlive           0          0             0x0
GiveUp              0          0             0x0
PmtuAger            1          0         0x9810C
DeadWait            0          0             0x0
Linger              0          0             0x0

iss: 3426928912  snduna: 3426929087  sndnxt: 3426929106     sndwnd:  16210
irs: 1337499386  rcvnxt: 1337499561  rcvwnd:      16210  delrcvwnd:    174

SRTT: 124 ms, RTTO: 1405 ms, RTV: 1281 ms, KRTT: 0 ms
minRTT: 108 ms, maxRTT: 300 ms, ACK hold: 200 ms
Status Flags: none
Option Flags: higher precendence, nagle, path mtu capable

Datagrams (max data segment is 1460 bytes):
Rcvd: 6 (out of order: 0), with data: 4, total data bytes: 174
Sent: 9 (retransmit: 0 fastretransmit: 0),with data: 5, total data bytes: 193

RT1#
RT1#sh ip int brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        192.168.1.1     YES NVRAM  up                    up
FastEthernet1/0        192.168.2.1     YES NVRAM  administratively down down
RT1#
10:20:53: RT: recursion error routing 192.168.2.2 - probable routing loop
10:20:55: RT: recursion error routing 192.168.2.2 - probable routing loop
10:20:58: RT: recursion error routing 192.168.2.2 - probable routing loop
10:21:02: BGP: topo global:IPv4 Unicast:base Scanning routing tables
10:21:02: BGP: topo global:IPv4 Multicast:base Scanning routing tables
10:21:03: RT: recursion error routing 192.168.2.2 - probable routing loop
10:21:15: RT: recursion error routing 192.168.2.2 - probable routing loop
RT1#
RT1#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP
       + - replicated route, % - next hop override

Gateway of last resort is not set

      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, FastEthernet0/0
L        192.168.1.1/32 is directly connected, FastEthernet0/0
B     192.168.2.0/24 [200/0] via 192.168.2.2, 00:01:30
RT1#
RT1#sh ip bgp
BGP table version is 3, local router ID is 192.168.2.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.1.0      0.0.0.0                  0         32768 i
*>i192.168.2.0      192.168.2.2              0    100      0 i
RT1#
RT1#sh ip bgp summary
BGP router identifier 192.168.2.1, local AS number 100
BGP table version is 3, main routing table version 3
2 network entries using 256 bytes of memory
2 path entries using 104 bytes of memory
2/2 BGP path/bestpath attribute entries using 248 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 608 total bytes of memory
BGP activity 2/0 prefixes, 2/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.2.2     4          100       5       6        3    0    0 00:02:19        1
RT1#
RT1#sh ip bgp neighbors 192.168.2.2
BGP neighbor is 192.168.2.2,  remote AS 100, internal link
  BGP version 4, remote router ID 192.168.2.254
  BGP state = Established, up for 00:02:19
  Last read 00:01:29, last write 00:00:38, hold time is 180, keepalive interval is 60 seconds
  Neighbor sessions:
    1 active, is multisession capable
    Session: 192.168.2.2
      Topology IPv4 Unicast
  Neighbor capabilities:
    Route refresh: advertised and received(new)
    Four-octets ASN Capability: advertised and received
    Address family IPv4 Unicast: advertised and received
    Multisession Capability: advertised and received
  Message statistics, state Established:
    InQ depth is 0
    OutQ depth is 0

                         Sent       Rcvd
    Opens:                  1          1
    Notifications:          0          0
    Updates:                2          2
    Keepalives:             3          2
    Route Refresh:          0          0
    Total:                  6          5
  Default minimum time between advertisement runs is 0 seconds

 For address family: IPv4 Unicast
  Session: 192.168.2.2 session 1
  BGP table version 3, neighbor version 3/0
  Output queue size : 0
  Index 1
  1 update-group member
                                 Sent       Rcvd
  Prefix activity:               ----       ----
    Prefixes Current:               1          1 (Consumes 52 bytes)
    Prefixes Total:                 1          1
    Implicit Withdraw:              0          0
    Explicit Withdraw:              0          0
    Used as bestpath:             n/a          1
    Used as multipath:            n/a          0

                                   Outbound    Inbound
  Local Policy Denied Prefixes:    --------    -------
    Bestpath from this peer:              1        n/a
    Total:                                1          0
  Number of NLRIs in the update sent: max 1, min 0
  Last detected as dynamic slow peer: never
  Dynamic slow peer recovered: never

  Address tracking is enabled, the RIB does not have a route to 192.168.2.2
  Connections established 1; dropped 0
  Last reset never
  Transport(tcp) path-mtu-discovery is enabled
  Graceful-Restart is disabled
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled
Mininum incoming TTL 0, Outgoing TTL 255
Local host: 192.168.2.1, Local port: 15732
Foreign host: 192.168.2.2, Foreign port: 179
Connection tableid (VRF): 0

Enqueued packets for retransmit: 1, input: 0  mis-ordered: 0 (0 bytes)

Event Timers (current time is 0x279CC):
Timer          Starts    Wakeups            Next
Retrans             9          4         0x28C50
TimeWait            0          0             0x0
AckHold             3          2             0x0
SendWnd             0          0             0x0
KeepAlive           0          0             0x0
GiveUp              0          0             0x0
PmtuAger            1          0         0x9810C
DeadWait            0          0             0x0
Linger              0          0             0x0

iss: 3426928912  snduna: 3426929087  sndnxt: 3426929106     sndwnd:  16210
irs: 1337499386  rcvnxt: 1337499561  rcvwnd:      16210  delrcvwnd:    174

SRTT: 124 ms, RTTO: 1405 ms, RTV: 1281 ms, KRTT: 22480 ms
minRTT: 108 ms, maxRTT: 300 ms, ACK hold: 200 ms
Status Flags: none
Option Flags: higher precendence, nagle, path mtu capable

Datagrams (max data segment is 1460 bytes):
Rcvd: 6 (out of order: 0), with data: 4, total data bytes: 174
Sent: 9 (retransmit: 4 fastretransmit: 0),with data: 5, total data bytes: 193

RT1#
10:21:37: RT: recursion error routing 192.168.2.2 - probable routing loop
10:21:43: RT: recursion error routing 192.168.2.2 - probable routing loop
10:22:02: BGP: topo global:IPv4 Unicast:base Scanning routing tables
10:22:02: BGP: topo global:IPv4 Multicast:base Scanning routing tables
10:22:22: RT: recursion error routing 192.168.2.2 - probable routing loop
10:22:41: RT: recursion error routing 192.168.2.2 - probable routing loop
RT1#
RT1#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP
       + - replicated route, % - next hop override

Gateway of last resort is not set

      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, FastEthernet0/0
L        192.168.1.1/32 is directly connected, FastEthernet0/0
B     192.168.2.0/24 [200/0] via 192.168.2.2, 00:02:40
RT1#
RT1#sh ip bgp
BGP table version is 3, local router ID is 192.168.2.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.1.0      0.0.0.0                  0         32768 i
*>i192.168.2.0      192.168.2.2              0    100      0 i
RT1#
RT1#sh ip bgp summary
BGP router identifier 192.168.2.1, local AS number 100
BGP table version is 3, main routing table version 3
2 network entries using 256 bytes of memory
2 path entries using 104 bytes of memory
2/2 BGP path/bestpath attribute entries using 248 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 608 total bytes of memory
BGP activity 2/0 prefixes, 2/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.2.2     4          100       5       8        3    0    0 00:03:29        1
RT1#
RT1#sh ip bgp neighbors 192.168.2.2
BGP neighbor is 192.168.2.2,  remote AS 100, internal link
  BGP version 4, remote router ID 192.168.2.254
  BGP state = Established, up for 00:03:29
  Last read 00:02:40, last write 00:00:01, hold time is 180, keepalive interval is 60 seconds
  Neighbor sessions:
    1 active, is multisession capable
    Session: 192.168.2.2
      Topology IPv4 Unicast
  Neighbor capabilities:
    Route refresh: advertised and received(new)
    Four-octets ASN Capability: advertised and received
    Address family IPv4 Unicast: advertised and received
    Multisession Capability: advertised and received
  Message statistics, state Established:
    InQ depth is 0
    OutQ depth is 0

                         Sent       Rcvd
    Opens:                  1          1
    Notifications:          0          0
    Updates:                2          2
    Keepalives:             5          2
    Route Refresh:          0          0
    Total:                  8          5
  Default minimum time between advertisement runs is 0 seconds

 For address family: IPv4 Unicast
  Session: 192.168.2.2 session 1
  BGP table version 3, neighbor version 3/0
  Output queue size : 0
  Index 1
  1 update-group member
                                 Sent       Rcvd
  Prefix activity:               ----       ----
    Prefixes Current:               1          1 (Consumes 52 bytes)
    Prefixes Total:                 1          1
    Implicit Withdraw:              0          0
    Explicit Withdraw:              0          0
    Used as bestpath:             n/a          1
    Used as multipath:            n/a          0

                                   Outbound    Inbound
  Local Policy Denied Prefixes:    --------    -------
    Bestpath from this peer:              1        n/a
    Total:                                1          0
  Number of NLRIs in the update sent: max 1, min 0
  Last detected as dynamic slow peer: never
  Dynamic slow peer recovered: never

  Address tracking is enabled, the RIB does not have a route to 192.168.2.2
  Connections established 1; dropped 0
  Last reset never
  Transport(tcp) path-mtu-discovery is enabled
  Graceful-Restart is disabled
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled
Mininum incoming TTL 0, Outgoing TTL 255
Local host: 192.168.2.1, Local port: 15732
Foreign host: 192.168.2.2, Foreign port: 179
Connection tableid (VRF): 0

Enqueued packets for retransmit: 2, input: 0  mis-ordered: 0 (0 bytes)

Event Timers (current time is 0x38E0C):
Timer          Starts    Wakeups            Next
Retrans            11          6         0x3EB90
TimeWait            0          0             0x0
AckHold             3          2             0x0
SendWnd             0          0             0x0
KeepAlive           0          0             0x0
GiveUp              0          0             0x0
PmtuAger            1          0         0x9810C
DeadWait            0          0             0x0
Linger              0          0             0x0

iss: 3426928912  snduna: 3426929087  sndnxt: 3426929144     sndwnd:  16210
irs: 1337499386  rcvnxt: 1337499561  rcvwnd:      16210  delrcvwnd:    174

SRTT: 124 ms, RTTO: 1405 ms, RTV: 1281 ms, KRTT: 44960 ms
minRTT: 108 ms, maxRTT: 300 ms, ACK hold: 200 ms
Status Flags: none
Option Flags: higher precendence, nagle, path mtu capable

Datagrams (max data segment is 1460 bytes):
Rcvd: 6 (out of order: 0), with data: 4, total data bytes: 174
Sent: 11 (retransmit: 6 fastretransmit: 0),with data: 7, total data bytes: 231

RT1#
10:23:02: BGP: topo global:IPv4 Unicast:base Scanning routing tables
10:23:02: BGP: topo global:IPv4 Multicast:base Scanning routing tables
10:23:03: BGP: 192.168.2.2 connection timed out 180248ms (last update) 180000ms (hold time)
10:23:03: BGP: 192.168.2.2 went from Established to Closing
10:23:03: %BGP-5-ADJCHANGE: neighbor 192.168.2.2 Down BGP Notification sent
10:23:03: %BGP-3-NOTIFICATION: sent to neighbor 192.168.2.2 4/0 (hold time expired) 0 bytes
10:23:03: BGP: ses global 192.168.2.2 (0x652A73FC:1) Send NOTIFICATION 4/0 (hold time expired) 0 bytes
10:23:03: RT: recursion error routing 192.168.2.2 - probable routing loop
10:23:03: BGP: 192.168.2.2 local error close after sending NOTIFICATION
10:23:03: BGP: nbr_topo global 192.168.2.2 IPv4 Unicast:base (0x652A73FC:1) NSF delete stale NSF not active
10:23:03: BGP: nbr_topo global 192.168.2.2 IPv4 Unicast:base (0x652A73FC:1) NSF no stale paths state is NSF not active
10:23:03: BGP: nbr_topo global 192.168.2.2 IPv4 Unicast:base (0x652A73FC:1) Resetting ALL counters.
10:23:03: BGP: 192.168.2.2 closing
10:23:03: RT: recursion error routing 192.168.2.2 - probable routing loop
10:23:03: BGP: nbr_topo global 192.168.2.2 IPv4 Unicast:base (0x652A73FC:1) Resetting ALL counters.
10:23:03: BGP: 192.168.2.2 went from Closing to Idle
10:23:03: %BGP_SESSION-5-ADJCHANGE: neighbor 192.168.2.2 IPv4 Unicast topology base removed from session  BGP Notification sent
10:23:03: BGP: ses global 192.168.2.2 (0x652A73FC:1) Removed topology IPv4 Unicast:base
10:23:03: BGP: ses global 192.168.2.2 (0x652A73FC:1) Removed last topology
10:23:03: BGP: nbr global 192.168.2.2 Active open failed - route to peer is invalid
10:23:03: BGP: nbr global 192.168.2.2 Active open failed - route to peer is invalid
10:23:03: RT: del 192.168.2.0 via 192.168.2.2, bgp metric [200/0]
10:23:03: RT: delete network route to 192.168.2.0/24
RT1#
RT1#sh ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP
       + - replicated route, % - next hop override

Gateway of last resort is not set

      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, FastEthernet0/0
L        192.168.1.1/32 is directly connected, FastEthernet0/0
RT1#
RT1#sh ip bgp
BGP table version is 4, local router ID is 192.168.2.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.1.0      0.0.0.0                  0         32768 i
RT1#
RT1#sh ip bgp summary
BGP router identifier 192.168.2.1, local AS number 100
BGP table version is 4, main routing table version 4
1 network entries using 128 bytes of memory
1 path entries using 52 bytes of memory
2/1 BGP path/bestpath attribute entries using 248 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 428 total bytes of memory
BGP activity 2/0 prefixes, 2/1 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.2.2     4          100       0       0        1    0    0 00:00:05 Idle
RT1#
RT1#sh ip bgp neighbors 192.168.2.2
BGP neighbor is 192.168.2.2,  remote AS 100, internal link
  BGP version 4, remote router ID 0.0.0.0
  BGP state = Idle
  Neighbor sessions:
    0 active, is multisession capable
  Default minimum time between advertisement runs is 0 seconds

 For address family: IPv4 Unicast
  BGP table version 4, neighbor version 1/4
  Output queue size : 0
  Index 0
                                 Sent       Rcvd
  Prefix activity:               ----       ----
    Prefixes Current:               0          0
    Prefixes Total:                 0          0
    Implicit Withdraw:              0          0
    Explicit Withdraw:              0          0
    Used as bestpath:             n/a          0
    Used as multipath:            n/a          0

                                   Outbound    Inbound
  Local Policy Denied Prefixes:    --------    -------
    Total:                                0          0
  Number of NLRIs in the update sent: max 1, min 0
  Last detected as dynamic slow peer: never
  Dynamic slow peer recovered: never

  Address tracking is enabled, the RIB does not have a route to 192.168.2.2
  Connections established 1; dropped 1
  Last reset 00:00:05, due to BGP protocol initialization
  Transport(tcp) path-mtu-discovery is enabled
  Graceful-Restart is disabled
  No active TCP connection
RT1#

Scenario #4
Scenario #4:
RT1#sh ip route

Gateway of last resort is not set

      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, FastEthernet0/0
L        192.168.1.1/32 is directly connected, FastEthernet0/0
      192.168.2.0/24 is variably subnetted, 3 subnets, 3 masks
B        192.168.2.0/24 [20/0] via 192.168.2.2, 00:00:23
C        192.168.2.0/30 is directly connected, FastEthernet1/0
L        192.168.2.1/32 is directly connected, FastEthernet1/0
RT1#
RT1#sh ip bgp
BGP table version is 3, local router ID is 192.168.2.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, x best-external
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.1.0      0.0.0.0                  0         32768 i
*> 192.168.2.0      192.168.2.2              0             0 200 i
RT1#
RT1#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
RT1(config)#int fa1/0
RT1(config-if)#shut
RT1(config-if)#end
RT1#
RT1#sh ip route

Gateway of last resort is not set

      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, FastEthernet0/0
L        192.168.1.1/32 is directly connected, FastEthernet0/0
RT1#
Posted by Yap Chin Hoong at 8:22 PM
Labels: ,

1 comment:

  1. AnonymousMarch 10, 2013 at 5:59 PM

    Dude. This is real good stuff . You have almost covered all the tricky issues which we may encounter on the Network Devices.

    Thank you very much for your dedication and logical analyzation. Keep up the Fantastic work.

    ReplyDelete

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