BGP Lab in GNS3

[5jgibbs]

I am using router1 to advertise 72.237.4.0 to two diffrent routers. I have the 67.*.*.* and the 4.*.*.*.

The 67 neighbor R3 can ping 72.237.4.1 but R4 cannot.. I see R4 as having a valid route "*" but not "*>". Here is some screenshots and the configs from R1,R3,R4.


Here is the GNS3 diagram..

http://www.cs.sunyit.edu/~gibbsj/network.png

R1 Config

R1#show run
Building configuration...

Current configuration : 1348 bytes
!
upgrade fpd auto
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R1
!
boot-start-marker
boot-end-marker
!
logging message-counter syslog
!
no aaa new-model
ip source-route
ip cef
!
!
!
!
no ipv6 cef
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
archive
log config
hidekeys
!
!
!
!
!
!
!
!
!
interface Loopback1
ip address 72.237.4.1 255.255.255.0
!
interface FastEthernet0/0
no ip address
shutdown
duplex half
!
interface FastEthernet1/0
ip address 67.216.14.171 255.255.255.248
duplex auto
speed auto
!
interface FastEthernet1/1
ip address 4.26.24.202 255.255.255.248
duplex auto
speed auto
!
interface FastEthernet2/0
no ip address
shutdown
duplex auto
speed auto
!
interface FastEthernet2/1
no ip address
shutdown
duplex auto
speed auto
!
router bgp 26808
no synchronization
bgp log-neighbor-changes
network 72.237.4.0 mask 255.255.255.0
neighbor 4.26.24.201 remote-as 3356
neighbor 67.216.14.169 remote-as 7828
no auto-summary
!
ip forward-protocol nd
ip route 72.237.4.0 255.255.255.0 Null0
no ip http server
no ip http secure-server
!
!
!
logging alarm informational
!
!
!
!
!
!
!
control-plane
!
!
!
!
!
!
!
gatekeeper
shutdown
!
!
line con 0
stopbits 1
line aux 0
stopbits 1
line vty 0 4
login
!
end

Router3

R3#show run
Building configuration...

Current configuration : 1448 bytes
!
upgrade fpd auto
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R3
!
boot-start-marker
boot-end-marker
!
logging message-counter syslog
!
no aaa new-model
ip source-route
ip cef
!
!
!
!
no ipv6 cef
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
archive
log config
hidekeys
!
!
!
!
!
!
!
!
!
interface FastEthernet0/0
no ip address
shutdown
duplex half
!
interface FastEthernet1/0
ip address 67.216.14.169 255.255.255.248
duplex auto
speed auto
!
interface FastEthernet1/1
no ip address
shutdown
duplex auto
speed auto
!
interface FastEthernet2/0
no ip address
shutdown
duplex auto
speed auto
!
interface FastEthernet2/1
ip address 4.4.4.4 255.255.255.0
duplex auto
speed auto
!
interface Ethernet3/0
no ip address
shutdown
duplex half
!
interface Ethernet3/1
no ip address
shutdown
duplex half
!
interface Ethernet3/2
no ip address
shutdown
duplex half
!
interface Ethernet3/3
no ip address
shutdown
duplex half
!
router bgp 7828
no synchronization
bgp log-neighbor-changes
neighbor 4.4.4.5 remote-as 7828
neighbor 67.216.14.171 remote-as 26808
no auto-summary
!
ip forward-protocol nd
no ip http server
no ip http secure-server
!
!
!
logging alarm informational
!
!
!
!
!
!
!
control-plane
!
!
!
!
!
!
!
gatekeeper
shutdown
!
!
line con 0
stopbits 1
line aux 0
stopbits 1
line vty 0 4
login
!
end

Router4

R4#show run
Building configuration...

Current configuration : 919 bytes
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R4
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
ip subnet-zero
!
!
ip cef
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface FastEthernet0/0
no ip address
shutdown
duplex half
!
interface FastEthernet1/0
ip address 4.4.4.5 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet1/1
ip address 4.4.5.4 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet2/0
no ip address
shutdown
duplex auto
speed auto
!
interface FastEthernet2/1
no ip address
shutdown
duplex auto
speed auto
!
router bgp 7828
no synchronization
bgp log-neighbor-changes
neighbor 4.4.4.4 remote-as 7828
neighbor 4.4.4.4 next-hop-self
no auto-summary
!
ip classless
no ip http server
!
!
!
!
!
!
!
!
!
line con 0
stopbits 1
line aux 0
stopbits 1
line vty 0 4
login
!
!
end


Here is another screen shot of show ip bgp and show ip route

http://www.cs.sunyit.edu/~gibbsj/ss.png

 

[unclerico]

Issue show ip bgp 72.237.4.0/24 on R4 and it will tell you why it is not being chosen. Think about how BGP determines if a route is valid and if it should be placed in the BGP table and then ultimately into the routing table. During the scan time BGP validates the reachability of the next hop for each prefix. If the next hop cannot be directly or recursively found then the prefix just sits there.

 

[unclerico]

Edit: one more thing, what is the rule when a route is received from an eBGP peer and then that route is advertised to an iBGP peer? What does not change by default? You have the option configured, but on the wrong BGP peer.