EdgeRouter – Border Gateway Protocol

Overview


Readers will learn how BGP is used and configured between two Autonomous Systems

BGP (Border Gateway Protocol)


Diagram Showing Two Different Autonomous Systems (AS)

R1: Router in AS 1

R2: Router in AS 2

Configuration


Note: These are the IP addresses of the two routers:

R1 IP address: 192.0.2.1
R2 IP address: 203.0.113.1
  • For the basic configuration of router R1 in AS 1, use the following commands to create a eBGP peer with router R2 in AS 2:
ubnt@R1:~$ configure  [edit]  ubnt@R1# set protocols bgp 1 parameters router-id 192.0.2.1  [edit]  ubnt@R1# set protocols bgp 1 neighbor 203.0.113.1 remote-as 2  [edit]  ubnt@R1# commit  [ protocols bgp 1 ]  Starting routing daemon: bgpd.  [edit]  ubnt@R1# save ; exit  Saving configuration to '/config/config.boot'...  Done  exit  
  • For the basic configuration of router R2 in AS 2, use the following commands to create a eBGP peer with router R1 in AS 1:
ubnt@R2:~$ configure  [edit]  ubnt@R2# set protocols bgp 2 parameters router-id 203.0.113.1  [edit]  ubnt@R2# set protocols bgp 2 neighbor 192.0.2.1 remote-as 1  [edit]  ubnt@R2# commit  [ protocols bgp 2 ]  Starting routing daemon: bgpd.  [edit]  ubnt@R2# save; exit  Saving configuration to '/config/config.boot'...  Done  exit  ubnt@R2:~$  

Peer Verification


Use the show ip bgp neighbors command to verify that the peer is established.

ubnt@R1:~$ show ip bgp neighbors   BGP neighbor is 203.0.113.1, remote AS 2, local AS 1, external link   BGP version 4, remote router ID 203.0.113.1   BGP state = Established, up for 00:00:13   Last read 00:55:04, hold time is 180, keepalive interval is 60 seconds   Neighbor capabilities:   4 Byte AS: advertised and received   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: 7 1   Notifications: 0 0   Updates: 0 0   Keepalives: 2 1   Route Refresh: 0 0   Capability: 0 0   Total: 9 2   Minimum time between advertisement runs is 30 seconds   Update source is 192.0.2.1   For address family: IPv4 Unicast   Community attribute sent to this neighbor(both)   0 accepted prefixes   Connections established 1; dropped 0   Last reset never   Local host: 192.0.2.1, Local port: 60047   Foreign host: 203.0.113.1, Foreign port: 179   Nexthop: 192.0.2.1   Nexthop global: fe80::de9f:dbff:fe29:5f7   Nexthop local: ::   BGP connection: non shared network   Read thread: on Write thread: off  

Learned Routes


The show command checks R1 for learned routes, and the configuration commands redistribute static routes on R2, so R1 will learn routes from R2.

  • Use the show ip route bgp command to check R1 for bgp routes learned from peer R2.
ubnt@R1:~$ show ip route bgp  ubnt@R1:~$  
  • No routes have been received because no routes have been redistributed. On R2, use the following commands to redistribute the static routes:
ubnt@R2:~$ configure  [edit]  ubnt@R2# set protocols bgp 2 redistribute static  [edit]  ubnt@R2# commit  [edit]  ubnt@R2# save; exit  Saving configuration to '/config/config.boot'...  Done  exit  
  • Check R1 again for bgp routes learned from peer R2.
ubnt@R1:~$ show ip route bgp  Codes: K - kernel route, C - connected, S - static, R - RIP, O - OSPF,   I - ISIS, B - BGP, > - selected route, * - FIB route  B>* 0.0.0.0/0 [20/0] via 203.0.113.1, eth2, 00:00:03  B>* 1.0.0.0/24 [20/0] via 203.0.113.1, eth2, 00:00:03
 

Full Internet Routes


Note: Receiving a full Internet routing table will consume significant amounts of memory; therefore, we do NOT recommend that you use BGP for full routes on the EdgeRouter Lite which only has 512MB of RAM.

Use the show ip route summary command to view the route summary.

admin@ubnt-bgp-test:~$ show ip route summary  Route Source Routes FIB  connected 3 3  static 3 2  ebgp 405543 405541  ibgp 0 0  ------  Totals 405549 405546

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