BGP Chapter 2 - Basic Configuration of BGP

Basic Configuration

Basic Commands

eBGP Basic Configuration

Interface Configuration 

R1#conifg

Configuring from terminal, memory, or network [terminal]? 

Enter configuration commands, one per line.  End with CNTL/Z.

R1(config)#int s0

R1(config-if)#ip address 12.1.1.1 255.255.255.0

R1(config-if)#no shut

R1(config-if)#^Z

R2#config

Configuring from terminal, memory, or network [terminal]? 

Enter configuration commands, one per line.  End with CNTL/Z.

R2(config)#

R2(config)#int s1

R2(config-if)#ip add 12.1.1.2 255.255.255.0

R2(config-if)#no sh

R2(config-if)#^Z

R2#ping 12.1.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 12.1.1.1, timeout is 2 seconds:

!!!!!

R1#ping 12.1.1.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 12.1.1.2, timeout is 2 seconds:

!!!!!

Basic Configuration of BGP 

R1#config

Configuring from terminal, memory, or network [terminal]? 

Enter configuration commands, one per line.  End with CNTL/Z.

R1(config)#router bgp ?

  <1-65535>  Autonomous system number   -----------------------> SEE THE RANGE OF AS 

R1(config)#router bgp 100 -----------------------------------------------> R1 is now member of AS 100

R1(config-router)#^Z

Dec  9 02:03:51.511: %SYS-5-CONFIG_I: Configured from console by console

R1#config 

Configuring from terminal, memory, or network [terminal]? 

Enter configuration commands, one per line.  End with CNTL/Z.

R1(config)#router bgp 200

BGP is already running; AS is 100------------------------------------------>Only one BGP AS can be configured on the device.

R1(config)#router bgp 100

R1(config-router)#neighbor 12.1.1.2 remote-as 200 ----------------------> Need to configure Neighbors manually using neighbor command.

R1(config-router)#^Z 

R2(config)#router bgp 200

R2(config-router)#neighbor 12.1.1.1 remote-as 100

R2(config-router)#^Z

R2#

Dec  9 02:05:43.391: %SYS-5-CONFIG_I: Configured from console by console

R2#

Dec  9 02:06:12.163: %BGP-5-ADJCHANGE: neighbor 12.1.1.1 Up 

R1#sh ip bgp summary 

BGP router identifier 12.1.1.1, local AS number 100

BGP table version is 1, main routing table version 1

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ        OutQ        Up/Down  State/PfxRcd

12.1.1.2          4   200          2               2        0                0             0         00:00:02        0

Configuration of loopback 0 on R2

R2(config)#int loopback 0

R2(config-if)#ip address 2.2.2.2 255.255.255.255

R2(config-if)#no sh

R2(config-if)#^Z

!!Advertise the network 2.2.2.2 /32

R2(config)#router bgp 200

R2(config-router)#netw

R2(config-router)#network 2.2.2.2 mask 255.255.255.255

R2(config-router)#^Z

!!Verifying route received at R1 

R1#sh ip bgp summary 

BGP router identifier 12.1.1.1, local AS number 100

BGP table version is 2, main routing table version 2

1 network entries using 117 bytes of memory

1 path entries using 52 bytes of memory

2/1 BGP path/bestpath attribute entries using 248 bytes of memory

1 BGP AS-PATH entries using 24 bytes of memory

0 BGP route-map cache entries using 0 bytes of memory

0 BGP filter-list cache entries using 0 bytes of memory

BGP using 441 total bytes of memory

BGP activity 1/0 prefixes, 1/0 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd

12.1.1.2        4   200       7       6        2    0    0 00:03:24        1

R1#sh ip bgp

BGP table version is 2, local router ID is 12.1.1.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

              r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path

*> 2.2.2.2/32       12.1.1.2                 0             0 200 i

R1#sh ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     2.0.0.0/32 is subnetted, 1 subnets

B       2.2.2.2 [20/0] via 12.1.1.2, 00:01:08

     12.0.0.0/24 is subnetted, 1 subnets

C       12.1.1.0 is directly connected, Serial0

R1#sh ip bgp neighbors 12.1.12.2

BGP neighbor is 12.1.1.2,  remote AS 200, external link

  BGP version 4, remote router ID 12.1.1.2

  BGP state = Established, up for 00:05:13

  Last read 00:00:13, last write 00:00:13, hold time is 180, keepalive interval is 60 seconds

  Neighbor capabilities:

    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:                  1          1

    Notifications:          0          0

    Updates:                0          1

    Keepalives:             7          7

    Route Refresh:          0          0

    Total:                  8          9

  Default minimum time between advertisement runs is 30 seconds

<output omitted>

Points to Remember

• Only one BGP AS can be configured on the device.

• Need to configure Neighbors manually using neighbor command.

• We need to advertise the networks .

• Ebgp neighbors should be directly connected. 

Basic Commands

• sh ip protocol

• sh ip bgp summary –shows the neighbors and the prefixes learned BGP Identifier Local ASN BGP table version

• sh ip route
• sh ip bgp
• sh ip bgp neigbhor x.x.x.x received-routes
• sh ip bgp neighbor x.x.x.x adverstied routes