BGP Load Balancing using EBGP Multihop and Loopback Interfaces

BGP Load Balancing using EBGP Multihop and Loopback Interfaces

RT1#sh ip bgp summary
BGP router identifier 1.1.1.1, local AS number 100
BGP table version is 2, main routing table version 2
1 network entries using 101 bytes of memory
1 path entries using 48 bytes of memory
1 BGP path attribute entries using 60 bytes of memory
1 BGP AS-PATH entries using 24 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 233 total bytes of memory
BGP activity 1/0 prefixes, 1/0 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
2.2.2.2         4   200       8       7        2    0    0 00:03:13        1
RT1#
RT1#sh ip bgp
BGP table version is 2, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.1.0      2.2.2.2                  0             0 200 i
RT1#
RT1#sh ip route

Gateway of last resort is not set

     1.0.0.0/32 is subnetted, 1 subnets
C       1.1.1.1 is directly connected, Loopback0
     2.0.0.0/32 is subnetted, 1 subnets
S       2.2.2.2 [1/0] via 12.12.12.2
                [1/0] via 21.21.21.2
     21.0.0.0/24 is subnetted, 1 subnets
C       21.21.21.0 is directly connected, Ethernet0/1
     12.0.0.0/24 is subnetted, 1 subnets
C       12.12.12.0 is directly connected, Ethernet0/0
B    192.168.1.0/24 [20/0] via 2.2.2.2, 00:02:49
RT1#
RT1#traceroute 192.168.1.1

Type escape sequence to abort.
Tracing the route to 192.168.1.1

  1 12.12.12.2 48 msec
    21.21.21.2 32 msec *
RT1#
RT1#traceroute 192.168.1.1

Type escape sequence to abort.
Tracing the route to 192.168.1.1

  1 21.21.21.2 36 msec
    12.12.12.2 12 msec *
RT1#

Notice about the * in the output of the traceroute commands? The following blog post will reveal the reason behind it. :-)
ICMP Destination Unreachable Rate Limiting - The reason behind U.U.U and .U.U.