Help with routing question between many routers in GNS3 BGP
I am trying to advertise an address block via BGP and I am mimicking our internet connection.
Here are some images
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
!
!
!
!
!
!
!
!
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!
!
!
!
!
!
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
A couple things catch my eye from the start:
1) there are no network statements in the R3 and R4 BGP configs. Someone needs to advertise the 4.4.4.0/24 network if you want other routers to reach it.
2) there's no IGP running between R3 and R4, yet they're in the same AS. Typically you would see an IGP running between routers in the same autonomous system to populate the routing table. (this isn't required to make your ping work though).
So, to fix this just enough to get ping working as indicated in your picture, you need to get two different routes added to the relevant routing tables. Lets start with advertising the 4.4.4.0/24 network.
Login to R3 and add the following:
config t router bgp 7828 network 4.4.4.0 mask 255.255.255.0 end clear ip bgp *
This should put the 4.4.4.0/24 prefix in R1's routing table:
4.0.0.0/8 is variably subnetted, 2 subnets, 2 masks B 4.4.4.0/24 [20/0] via 67.216.14.169, 00:00:02
Now, we need to add the 72.237.4.0/24 network to R4's routing table. R1 is advertising it just fine, but because R3 and R4 are iBGP neighbors, R3 is just passing the route it learned along to R4. However, this means the route still has a next hop of 67.216.14.171, which according to the show ip route screen shot you provided, R4 has no idea how to get to that network. There are a couple ways to fix this, here's one way:
Log in to R3 and run the following commands:
config t router bgp 7828 neighbor 4.4.4.5 next-hop-self end clear ip bgp *
Now R3 should replace the next hop of BGP routes it advertises to R4 with it's own IP address. You can see this with a show ip route command on R4:
72.0.0.0/24 is subnetted, 1 subnets B 72.237.4.0 [200/0] via 4.4.4.4, 00:06:55
Your ping should work now.
R4#ping 72.237.4.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 72.237.4.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 36/52/88 ms
Here is another screen shot of show ip bgp and show ip route
http://www.cs.sunyit.edu/~gibbsj/ss.png