NETWORK ENGINEER STUFF: BGP Chapter 22

Route learned from an iBGP neighbor cannot be forwarded to other iBGP neighbor.

Solution for this are :-

1) Full Mesh iBGP

2) Route Reflector

3) Confederation

Lets focus on 1st Solution in this chapter

1) Full Mesh iBGP

Making full mesh of iBGP peers even if they are not directly connected .

So that each iBGP router will have BGP routes for AS.

The requirement of fully meshed iBGP means that, for n BGP speakers (within the same AS), there will be n(n-1)/2 iBGP peering sessions.

For example, if there are 10 BGP speakers in a particular AS, then there must be 10(10-1)/2 iBGP sessions, which is 45 peering sessions.

This may not scale well in ASs that have large number of iBGP peers.

So the solution to this are the other two methods :-

Route Reflector and Confederation.

LAB

=========

Basic Configuration

=======================

R1
===============
config t
hostname R1
interface eth1/0
ip add 12.1.1.1 255.255.255.0
no shut
exit
interface eth1/1
ip add 13.1.1.1 255.255.255.0
no shut
exit
int loopback 0
ip address 1.1.1.1 255.255.255.255
int loopback 1
ip address 10.0.0.1 255.255.255.0
ip route 2.2.2.2 255.255.255.255 12.1.1.2
ip route 3.3.3.3 255.255.255.255 13.1.1.3
exit
exit

R2
===============
config t
hostname R2
interface eth1/0
ip add 12.1.1.2 255.255.255.0
no shut
exit
int loopback 0
ip address 2.2.2.2 255.255.255.255
int loopback 1
ip address 20.0.0.1 255.255.255.0
ip route 1.1.1.1 255.255.255.255 12.1.1.1
ip route 3.3.3.3 255.255.255.255 12.1.1.1
exit
exit

R3
===============
config t
hostname R3
interface eth1/1
ip add 13.1.1.3 255.255.255.0
no shut
exit
int loopback 0
ip address 3.3.3.3 255.255.255.255
int loopback 1
ip address 30.0.0.1 255.255.255.0
ip route 1.1.1.1 255.255.255.255 13.1.1.1
ip route 2.2.2.2 255.255.255.255 13.1.1.1
exit
exit

BGP Configuration on R1
========================
config t
router bgp 100
neighbor amar peer-group
neighbor amar remote-as 100
neighbor amar update-source loopback 0
neighbor amar password cisco123
neighbor 2.2.2.2 peer-group amar
neighbor 3.3.3.3 peer-group amar
exit
exit

BGP Configuration on R2
==========================
config t
router bgp 100
neighbor 1.1.1.1 remote-as 100
neighbor 1.1.1.1 update-source loopback 0
neighbor 1.1.1.1 password cisco123
exit
exit

BGP Configuration on R3
==========================
config t
router bgp 100
neighbor 1.1.1.1 remote-as 100
neighbor 1.1.1.1 update-source loopback 0
neighbor 1.1.1.1 password cisco123
exit
exit

===================
R1#sh ip bgp summary
BGP router identifier 1.1.1.1, 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
2.2.2.2         4          100       6       7        1    0    0 00:02:51        0
3.3.3.3         4          100       5       4        1    0    0 00:02:39        0
R1#

R2#sh ip bgp summary
BGP router identifier 20.1.1.1, 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
1.1.1.1         4          100       7       7        1    0    0 00:03:15        0
R2#

R3#sh ip bgp summary
BGP router identifier 30.1.1.1, 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
1.1.1.1         4          100       5       6        1    0    0 00:03:24        0
R3#

========================================================================
R1

config t
router bgp 100
network 10.0.0.0 mask 255.255.255.0
exit
exit
wr

R2

config t
router bgp 100
network 20.0.0.0 mask 255.255.255.0
exit
exit
wr

R3

config t
router bgp 100
network 30.0.0.0 mask 255.255.255.0
exit
exit
wr

R1#sh ip bgp
BGP table version is 6, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
*> 10.0.0.0/24      0.0.0.0                  0         32768 i
*>i 20.0.0.0/24      2.2.2.2                  0    100      0 i
*>i 30.0.0.0/24      3.3.3.3                  0    100      0 i

R2#sh ip bgp
BGP table version is 5, local router ID is 20.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
*>i 10.0.0.0/24      1.1.1.1                  0    100      0 i
*> 20.0.0.0/24      0.0.0.0                  0         32768 i

R3#sh ip bgp
BGP table version is 3, local router ID is 30.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
*>i 10.0.0.0/24      1.1.1.1                  0    100      0 i
*> 30.0.0.0/24      0.0.0.0                  0         32768 i

Lets try full mesh iBGP Peering

R2
config t
router bgp 100
neighbor 3.3.3.3 remote-as 100
neighbor 3.3.3.3 update-source loopback 0
neighbor 3.3.3.3 password cisco123
exit
exit

R3
config t
router bgp 100
neighbor 2.2.2.2 remote-as 100
neighbor 2.2.2.2 update-source loopback 0
neighbor 2.2.2.2 password cisco123
exit
exit

R2#sh ip bgp summary
BGP router identifier 20.1.1.1, local AS number 100
BGP table version is 6, main routing table version 6
3 network entries using 432 bytes of memory
3 path entries using 240 bytes of memory
2/2 BGP path/bestpath attribute entries using 272 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 944 total bytes of memory
BGP activity 3/0 prefixes, 4/1 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer InQ OutQ Up/Down State/PfxRcd
1.1.1.1         4          100      43      46        6    0    0 00:35:31        1
3.3.3.3         4          100       7       7        6    0    0 00:00:15        1

R3#sh ip bgp summary
BGP router identifier 30.1.1.1, local AS number 100
BGP table version is 4, main routing table version 4
3 network entries using 432 bytes of memory
3 path entries using 240 bytes of memory
2/2 BGP path/bestpath attribute entries using 272 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 944 total bytes of memory
BGP activity 3/0 prefixes, 3/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer InQ OutQ Up/Down State/PfxRcd
1.1.1.1         4          100      45      44        4    0    0 00:35:34        1
2.2.2.2         4          100       7       7        4    0    0 00:00:31        1
R3#

R2#sh ip bgp
BGP table version is 6, local router ID is 20.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
*>i 10.0.0.0/24      1.1.1.1                  0    100      0 i
*> 20.0.0.0/24      0.0.0.0                  0         32768 i
*>i 30.0.0.0/24      3.3.3.3                  0    100      0 i
R2#
R2#
R2#ping 30.0.0.1 source loopback0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 30.0.0.1, timeout is 2 seconds:
Packet sent with a source address of 2.2.2.2
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/34/44 ms

R3#sh ip bgp
BGP table version is 4, local router ID is 30.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
              x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
*>i 10.0.0.0/24      1.1.1.1                  0    100      0 i
*>i 20.0.0.0/24      2.2.2.2                  0    100      0 i
*> 30.0.0.0/24      0.0.0.0                  0         32768 i
R3#
R3#
R3#ping 20.0.0.1 sou
R3#ping 20.0.0.1 source loopback 0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 20.0.0.1, timeout is 2 seconds:
Packet sent with a source address of 3.3.3.3
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/33/64 ms

Thanks for Reading !!

amartechstuff