BGP-iBGP

R1 Config
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface FastEthernet0/0
 ip address 12.1.1.1 255.255.255.0
 duplex auto
 speed auto
!
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.0
 neighbor 12.1.1.2 remote-as 100
 neighbor 12.1.1.3 remote-as 100
 neighbor 12.1.1.4 remote-as 100
 no auto-summary
R2 Config
interface Loopback0
 ip address 2.2.2.2 255.255.255.0
!
interface FastEthernet0/0
 ip address 12.1.1.2 255.255.255.0
 duplex auto
 speed auto
!
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 network 2.2.2.0 mask 255.255.255.0
 neighbor 12.1.1.1 remote-as 100
 neighbor 12.1.1.3 remote-as 100
 neighbor 12.1.1.4 remote-as 100
 no auto-summary
!

R3 Config
interface Loopback0
 ip address 3.3.3.3 255.255.255.0
!
interface FastEthernet0/0
 ip address 12.1.1.3 255.255.255.0
 duplex auto
 speed auto
!
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 network 3.3.3.0 mask 255.255.255.0
 neighbor 12.1.1.1 remote-as 100
 neighbor 12.1.1.2 remote-as 100
 neighbor 12.1.1.4 remote-as 100
 no auto-summary
!
R4 Config
interface Loopback0
 ip address 4.4.4.4 255.255.255.0
!
interface FastEthernet0/0
 ip address 12.1.1.4 255.255.255.0
 duplex auto
 speed auto
!
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 network 4.4.4.0 mask 255.255.255.0
 neighbor 12.1.1.1 remote-as 100
 neighbor 12.1.1.2 remote-as 100
 neighbor 12.1.1.3 remote-as 100
 no auto-summary
!
*Mar  1 00:05:28.631: BGP: 12.1.1.1 went from Idle to Active
*Mar  1 00:05:28.639: BGP: 12.1.1.1 open active delayed 34036ms (35000ms max, 28% jitter)
*Mar  1 00:05:52.055: BGP: 12.1.1.1 passive open to 12.1.1.4
*Mar  1 00:05:52.055: BGP: 12.1.1.1 went from Active to Idle
*Mar  1 00:05:52.055: BGP: 12.1.1.1 went from Idle to Connect
*Mar  1 00:05:52.063: BGP: 12.1.1.1 rcv message type 1, length (excl. header) 26
*Mar  1 00:05:52.067: BGP: 12.1.1.1 rcv OPEN, version 4, holdtime 180 seconds
*Mar  1 00:05:52.067: BGP: 12.1.1.1 went from Connect to OpenSent
*Mar  1 00:05:52.067: BGP: 12.1.1.1 sending OPEN, version 4, my as: 100, holdtime 180 seconds
*Mar  1 00:05:52.067: BGP: 12.1.1.1 rcv OPEN w/ OPTION parameter len: 16
*Mar  1 00:05:52.067: BGP: 12.1.1.1 rcvd OPEN w/ optional parameter type 2 (Capability) len 6
*Mar  1 00:05:52.071: BGP: 12.1.1.1 OPEN has CAPABILITY code: 1, length 4
*Mar  1 00:05:52.071: BGP: 12.1.1.1 OPEN has MP_EXT CAP for afi/safi: 1/1
*Mar  1 00:05:52.071: BGP: 12.1.1.1 rcvd OPEN w/ optional parameter type 2 (Capability) len 2
*Mar  1 00:05:52.071: BGP: 12.1.1.1 OPEN has CAPABILITY code: 128, length
*Mar  1 00:05:52.071: BGP: 12.1.1.1 OPEN has ROUTE-REFRESH capability(old) for all address-families
*Mar  1 00:05:52.075: BGP: 12.1.1.1 rcvd OPEN w/ optional parameter type 2 (Capability) len 2
*Mar  1 00:05:52.075: BGP: 12.1.1.1 OPEN has CAPABILITY code: 2, length 0
*Mar  1 00:05:52.075: BGP: 12.1.1.1 OPEN has ROUTE-REFRESH capability(new) for all address-families
*Mar  1 00:05:52.075: BGP: 12.1.1.1 went from OpenSent to OpenConfirm
*Mar  1 00:05:52.079: BGP: 12.1.1.1 send message type 1, length (incl. header) 45
*Mar  1 00:05:52.151: BGP: 12.1.1.1 went from OpenConfirm to Established

==============================================================================

R1#show ip bgp neighbors 12.1.1.3
BGP neighbor is 12.1.1.3,  remote AS 100, internal link
  BGP version 4, remote router ID 3.3.3.3
  BGP state = Established, up for 00:08:15
  Last read 00:00:15, last write 00:00:15, hold time is 180, keepalive interval is 60 seconds
  Neighbor capabilities:
    Route refresh: advertised and received(old & new)
    Address family IPv4 Unicast: advertised and received
  Message statistics:
    InQ depth is 0
    OutQ depth is 0
                         Sent       Rcvd
    Opens:                  1          1
    Notifications:          0          0
    Updates:                1          1
    Keepalives:            11         11
    Route Refresh:          0          0
    Total:                 13         13
  Default minimum time between advertisement runs is 0 seconds

 For address family: IPv4 Unicast
  BGP table version 5, neighbor version 5/0
 Output queue size : 0
  Index 1, Offset 0, Mask 0x2
  1 update-group member
                                 Sent       Rcvd
  Prefix activity:               ----       ----
    Prefixes Current:               1          1 (Consumes 52 bytes)
    Prefixes Total:                 1          1
    Implicit Withdraw:              1          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 iBGP peer:              3        n/a
    Total:                                3          0
  Number of NLRIs in the update sent: max 1, min 1

  Connections established 1; dropped 0
  Last reset never
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: 12.1.1.1, Local port: 41981
Foreign host: 12.1.1.3, Foreign port: 179







R2 Config
router bgp 100
neighbor 25.1.1.5 remote-as 54

R2(config-router)#do show ip bgp nei 25.1.1.5
BGP neighbor is 25.1.1.5,  remote AS 54, external link
  BGP version 4, remote router ID 25.1.1.5
  BGP state = Established, up for 00:02:34
  Last read 00:00:20, last write 00:00:33, hold time is 180, keepalive interval is 60 seconds
  Neighbor capabilities:
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 1
Local host: 25.1.1.2, Local port: 13280
Foreign host: 25.1.1.5, Foreign port: 179