Routing – block route being advertised to SP

bgpisprouting

I have a network that resembles this

CUSTOMER - BT - SPRINT
           BT - CISCO

customer loopback 192.168.10.1 customer loopback1 192.168.1.1

BT loopback 192.168.50.1

CISCO loopback 192.168.100.1

SPRINT loopback 192.168.150.1

customer is connected to BT

BT is connected to SPRINT and CISCO

I am using Community values and I want to block the advertisement of 192.168.1.1/24 to SPRINT but allow it to appear in Cisco

This was my failed attempt:

CUSTOMER:
ip prefix-list ROUTE 192.168.1.0/24
neighbor 2.2.2.2 (bt) route-map BLOCKSPRINT out
neighbor 2.2.2.2 send-community

route-map BLOCKSPRINT p 10
match ip add prefix-list ROUTE
set community 500:500
route-map BLOCKSPRINT p 20

BT
ip prefix-list CISCO 192.168.150.0/24
ip community-list 1 500:500 
neighbor 1.1.1.1 Peer-CUST in
neighbor 1.1.1.1 send-communities
neighbor 3.3.3.3 send-communities

route-map Peer-CUST p 10
match ip add prefix-list CISCO
match community 1
set community no-advertise
route-map Peer-CUST p 20

The address still shows up on the SPRINT router.

Best Answer

You have BT sending the route to Sprint with the no-advertise community so that the Sprint router will not advertise it. BT needs to filter the prefix to Sprint. Something like:

neighbor 3.3.3.3 distribute-list 1 out 
!
access-list 1 deny 192.168.1.1 0.0.0.255
access-list 1 permit any

or

neighbor 3.3.3.3 route-map BLOCKSPRINT out 
!
access-list 1 deny 192.168.1.1 0.0.0.255
access-list 1 permit any
!
route-map BLOCKSPRINT permit 10 
 match ip address 1

Related Solutions

IPv6 Routing – Smallest IPv6 Block Advertised?

Yes. Nobody will advertise any network smaller than a /48. The same thing is in IPv4; no ISP will advertise any network smaller than a /24.

The problem is the sheer number of routes that would generate on the Internet by advertising networks smaller than a /48. Even at /48 with the current global address range of 2000::/3, that translates to 35,184,372,088,832 possible routes.

In fact, IANA had a rule that nobody (even individuals) should get networks smaller than /48. The ISPs eventually overruled that for individuals, giving them /56. Each site is supposed to have at least a /56, and a company gets at least a /48 which the company can advertise. If you wish to advertise individual sites, they each need a /48 (or a /56 out of separate /48s).

You can go to the RIR and get a smaller mask. For instance, we got a /32 from each RIR.

Routing – Quagga bgp advertisment stop after peer restart

By the data that you give us, this one is an interesting part. Unless you had change the neighbors for your safety, and put the conf here, i think you need to explaind why your iBGP neighbor has the same IP address of your UPDATE SOURCE? This one is like if your iBGP share your same host.

neighbor 1.1.1.1 description "R101 BGP interconnect"
neighbor 1.1.1.1 update-source 1.1.1.1
neighbor 1.1.1.1 next-hop-self
neighbor 1.1.1.1 send-community both
neighbor 1.1.1.1 soft-reconfiguration inbound

neighbor 1.1.1.2 description "R102 BGP interconnect"
neighbor 1.1.1.2 update-source 1.1.1.2
neighbor 1.1.1.2 next-hop-self
neighbor 1.1.1.2 send-community both
neighbor 1.1.1.2 soft-reconfiguration inbound

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