Let's explore few concepts of BGP and how to configure it on the Nokia 7750 SR
Border gateway protocol is mainly used by Service Providers to carry the huge routing information between different Autonomous Systems.
It uses the well-known TCP port number 179. BGP uses TCP protocol for authenticating its peer router session.
There are two types of BGP as listed below
1. IBGP (Internal BGP used to share routing information within its own AS)
2. Ebgp (External BGP used to share routing information between 2 different AS)
Let's explore how to configure BGP types as per the below topology. IGP is pre-configured as per topology.
1. IBGP configuration between PE01 to PE02
Forming IBGP between Router system IP/Loopback address is a best practice for family ipv4.
why are we configuring internal BGP on SYSTEM/LOOPBACK IP?
If we configure the adjacency using the physical interface for the ipv4 family it will lead to failure if that particular interface goes down.
Even if we have an alternate path to reach the router it will not be useful if we configure it in the physical interface once the interface goes down.
PE01: 10.10.10.1
PE02: 10.10.10.2
PE01:
/configure router bgp autonomous
/configure router bgp group "ibgp-internal"
/configure router bgp group "ibgp-internal" neighbor 10.10.10.2
/configure router bgp group "ibgp-internal" neighbor 10.10.10.2 type internal
/configure router bgp group "ibgp-internal" neighbor 10.10.10.2 peer-as 65001
PE02:
/configure router bgp autonomous
/configure router bgp group "ibgp-internal"
/configure router bgp group "ibgp-internal" neighbor 10.10.10.1
/configure router bgp group "ibgp-internal" neighbor 10.10.10.1 type internal
/configure router bgp group "ibgp-internal" neighbor 10.10.10.1 peer-as 65001
To bring up the BGP one more configuration is required. Need to configure the autonomous system to bring the session up.
/configure router autonomous-system 65001
Let's verify the BGP output:
PE01# show router BGP summary all
===================================================================
BGP Summary
===================================================================
Neighbor
Description
ServiceId AS PktRcvd InQ Up/Down State|Rcv/Act/Sent (Addr Family) PktSent OutQ
-------------------------------------------------------------------------------------------------------------------
10.10.10.2
Def. Instance 65001 9 0 00h03m22s 0/0/0 (IPv4) 9 0
-------------------------------------------------------------------------------------------------------------------
By default in Nokia SR, it will form the family IPV4 neighborship if we don't configure any family under the BGP configuration hierarchy.
2. eBGP configuration between PE01 and CE01
External BGP configured between PE01 and CE01 router. CE01 advertise prefixes to PE01 and it propagates it's further to PE02 via pre-configured IBGP session.
PE01:
/configure router bgp group "ebgp-external"
/configure router bgp group "ebgp-external" neighbor 10.1.5.5
/configure router bgp group "ebgp-external" neighbor 10.1.5.5 type external
/configure router bgp group "ebgp-external" neighbor 10.1.5.5 peer-as 65002
CE01:
/configure router bgp group "ebgp-external"
/configure router bgp group "ebgp-external" neighbor 10.1.5.1
/configure router bgp group "ebgp-external" neighbor 10.1.5.1 type external
/configure router bgp group "ebgp-external" neighbor 10.1.5.1 peer-as 65001
CE advertising its system IP to PE01:
CE01# show router BGP summary all
====================================================================
BGP Summary
====================================================================
Neighbor
Description
ServiceId AS PktRcvd InQ Up/Down State|Rcv/Act/Sent (Addr Family) PktSent OutQ
------------------------------------------------------------------------------------------------------------------
10.1.5.1
Def. Instance 65001 53 0 00h03m30s 0/0/1 (IPv4) 55 0
------------------------------------------------------------------------------------------------------------------
Routes received on PE01 router from CE:
PE01# show router bgp routes
=========================================================================
BGP Router ID:10.10.10.1 AS:65001 Local AS:65001
=========================================================================
Legend -
Status codes : u - used, s - suppressed, h - history, d - decayed, * - valid
l - leaked, x - stale, > - best, b - backup, p - purge
Origin codes : i - IGP, e - EGP, ? - incomplete
=========================================================================
BGP IPv4 Routes
=========================================================================
Flag Network LocalPref MED
Nexthop (Router) Path-Id Label
As-Path
-------------------------------------------------------------------------------
u*>i 10.10.10.5/32 None None
10.1.5.5 None -
65002
-------------------------------------------------------------------------------
Routes : 1
=========================================================================
PE01 receiving the route from its external BGP and advertises it to PE02 via IBGP.
PE01# show router bgp summary all
=========================================================================BGP Summary
=========================================================================Neighbor
Description
ServiceId AS PktRcvd InQ Up/Down State|Rcv/Act/Sent (Addr Family) PktSent OutQ
------------------------------------------------------------------------------------------------------------------
10.1.5.5
Def. Instance 65002 35 0 00h03m52s 1/1/1 (IPv4) 60 0
10.10.10.2
Def. Instance 65001 50 0 00h23m30s 0/0/1 (IPv4) 50 0
-------------------------------------------------------------------------------------------------------------------
From the above output, we can see 10.1.5.5 is receiving a route via external BGP and advertising it back to its iBGP peer of 10.10.10.2 PE02.
In our, Next Post let's analyze the routes on the PE02 router and how it's installing it in the routing table.
