Basic EBGP configuration

Basic EBGP configuration between two Cisco IOS routers:

Here is the basic external BGP configuration between two routers.

(We announced loopback IP addresses on both routers for testing)

First router:

interface Loopback4

 ip address 4.4.4.4 255.255.255.255

!

interface FastEthernet1/0

 ip address 192.168.45.4 255.255.255.0

 !

router bgp 4

 no synchronization

 bgp log-neighbor-changes

 network 4.4.4.4 mask 255.255.255.255

 neighbor 192.168.45.5 remote-as 5

 no auto-summary

Second Router:

interface Loopback5

 ip address 5.5.5.5 255.255.255.255

!

interface FastEthernet0/0

 ip address 192.168.45.5 255.255.255.0

!

router bgp 5

 no synchronization

 bgp log-neighbor-changes

 network 5.5.5.5 mask 255.255.255.255

 neighbor 192.168.45.4 remote-as 4

 no auto-summary

BGP is up:

R4#show ip bgp summary

BGP router identifier 192.168.0.4, local AS number 4

BGP table version is 3, main routing table version 3

2 network entries using 240 bytes of memory

2 path entries using 104 bytes of memory

3/2 BGP path/bestpath attribute entries using 372 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

Bitfield cache entries: current 1 (at peak 1) using 32 bytes of memory

BGP using 772 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

192.168.45.5    4     5      10      10        3    0    0 00:06:22        1

BGP table is created:

R4#show ip bgp

BGP table version is 3, local router ID is 192.168.0.4

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

*> 4.4.4.4/32       0.0.0.0                  0         32768 i

*> 5.5.5.5/32       192.168.45.5             0             0 5 i

Routing table entry for remote route shows the BGP route:

R4#show ip route 5.5.5.5

Routing entry for 5.5.5.5/32

  Known via "bgp 4", distance 20, metric 0

  Tag 5, type external

  Last update from 192.168.45.5 00:07:25 ago

  Routing Descriptor Blocks:

  * 192.168.45.5, from 192.168.45.5, 00:07:25 ago

      Route metric is 0, traffic share count is 1

      AS Hops 1

      Route tag 5

Reachability test:

R4#ping 5.5.5.5 source 4.4.4.4

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:

Packet sent with a source address of 4.4.4.4

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/36/68 ms