4) Verification and Testing of the Configurations

R0_AS_200#sho ip bgp summary
BGP router identifier 200.20.20.1, local AS number 200
BGP table version is 44, main routing table version 44
16 network entries using 1552 bytes of memory
21 path entries using 756 bytes of memory
11 BGP path attribute entries using 660 bytes of memory
5 BGP AS-PATH entries using 120 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 3088 total bytes of memory
BGP activity 24/8 prefixes, 41/20 paths, scan interval 60 secs

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
12.123.50.1 4 30 109 96 44 0 0 00:54:37 9
60.50.10.1 4 100 101 95 44 0 0 00:54:33 7

R0_AS_200#sho ip bgp neighbors 12.123.50.1 routes
BGP table version is 44, local router ID is 200.20.20.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
*> 30.30.11.0/24 12.123.50.1 0 0 30 ?
*> 30.30.12.0/24 12.123.50.1 0 30 ?
*> 50.50.11.0/24 12.123.50.1 0 30 50 ?
*> 50.50.12.0/24 12.123.50.1 0 30 50 ?
* 192.168.10.0 12.123.50.1 0 30 50 192 i
* 192.168.20.0 12.123.50.1 0 30 50 192 ?
* 192.168.30.0 12.123.50.1 0 30 50 192 ?
* 192.168.40.0 12.123.50.1 0 30 50 192 ?
* 192.168.50.0 12.123.50.1 0 30 50 192 ?

Total number of prefixes 9

R0_AS_200#sho ip bgp neighbors 60.50.10.1 routes
BGP table version is 44, local router ID is 200.20.20.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
*> 100.100.11.0/24 60.50.10.1 0 0 100 ?
*> 100.100.12.0/24 60.50.10.1 0 100 ?
*> 192.168.10.0 60.50.10.1 0 100 192 i
*> 192.168.20.0 60.50.10.1 0 100 192 ?
*> 192.168.30.0 60.50.10.1 0 100 192 ?
*> 192.168.40.0 60.50.10.1 0 100 192 ?
*> 192.168.50.0 60.50.10.1 0 100 192 ?

Total number of prefixes 7

*** By leaving the BGP attributes to its default behavior, R0 will choose to go through AS 100 to get to R5 because the AS path is lesser compare to the other path.

R0_AS_200#sho ip route bgp
50.0.0.0/24 is subnetted, 2 subnets
B 50.50.11.0 [20/0] via 12.123.50.1, 00:55:23
B 50.50.12.0 [20/0] via 12.123.50.1, 00:55:23
100.0.0.0/24 is subnetted, 2 subnets
B 100.100.11.0 [20/0] via 60.50.10.1, 00:55:20
B 100.100.12.0 [20/0] via 60.50.10.1, 00:55:20
B 192.168.30.0/24 [20/0] via 60.50.10.1, 00:55:20
B 192.168.10.0/24 [20/0] via 60.50.10.1, 00:55:20
B 192.168.40.0/24 [20/0] via 60.50.10.1, 00:55:20
B 192.168.20.0/24 [20/0] via 60.50.10.1, 00:55:20
B 192.168.50.0/24 [20/0] via 60.50.10.1, 00:55:20
30.0.0.0/24 is subnetted, 2 subnets
B 30.30.11.0 [20/0] via 12.123.50.1, 00:55:23
B 30.30.12.0 [20/0] via 12.123.50.1, 00:55:23

*** Notice R0 routing table, R0 is receiving advertisement for the network 192.168.0.0 from R1 and R6, but R6 advertisements ended up in R0 routing table this is because R0 sees a shorter path going to R5 via R6.

R0_AS_200#sho ip bgp neighbors 60.50.10.1 advertised-routes
BGP table version is 44, local router ID is 200.20.20.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
*> 200.20.20.0 0.0.0.0 0 32768 i
*> 200.20.30.0 0.0.0.0 0 32768 ?
*> 200.20.40.0 0.0.0.0 0 32768 ?
*> 200.20.50.0 0.0.0.0 0 32768 ?
*> 200.20.60.0 0.0.0.0 0 32768 ?

R0_AS_200#sho ip bgp neighbors 12.123.50.1 advertised-routes
BGP table version is 44, local router ID is 200.20.20.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
*> 200.20.20.0 0.0.0.0 0 32768 i
*> 200.20.30.0 0.0.0.0 0 32768 ?
*> 200.20.40.0 0.0.0.0 0 32768 ?
*> 200.20.50.0 0.0.0.0 0 32768 ?
*> 200.20.60.0 0.0.0.0 0 32768 ?

*** R0 is advertising the same exact networks to both R1 and R6

R0_AS_200#ping ip 192.168.10.1 so 200.20.20.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.10.1, timeout is 2 seconds:
Packet sent with a source address of 200.20.20.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 264/360/456 ms

R0_AS_200#traceroute ip

Target IP address: 192.168.10.1
Source address: 200.20.20.1
Numeric display [n]:
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Port Number [33434]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Type escape sequence to abort.
Tracing the route to 192.168.10.1

1 60.50.10.1 116 msec 48 msec 144 msec --> ISP AS 100
2 100.100.10.2 216 msec 360 msec 216 msec
3 60.50.10.6 336 msec * 360 msec
R0_AS_200#

*** Connectivity tests: ping and traceroutes to R5

************************************************************************************

R5_AS_192#sho ip bgp summary
BGP router identifier 192.168.10.1, local AS number 192
BGP table version is 33, main routing table version 33
16 network entries using 1552 bytes of memory
21 path entries using 756 bytes of memory
11 BGP path attribute entries using 660 bytes of memory
5 BGP AS-PATH entries using 120 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 3088 total bytes of memory
BGP activity 24/8 prefixes, 33/12 paths, scan interval 60 secs

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
50.50.13.1 4 50 89 88 33 0 0 01:06:35 9
60.50.10.5 4 100 78 81 33 0 0 01:00:00 7



R5_AS_192#sho ip bgp neighbors 50.50.13.1 routes
BGP table version is 33, local router ID is 192.168.10.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
*> 30.30.11.0/24 50.50.13.1 0 50 30 ?
*> 30.30.12.0/24 50.50.13.1 0 50 30 ?
*> 50.50.11.0/24 50.50.13.1 0 0 50 ?
*> 50.50.12.0/24 50.50.13.1 0 50 ?
* 200.20.20.0 50.50.13.1 0 50 30 200 i
* 200.20.30.0 50.50.13.1 0 50 30 200 ?
* 200.20.40.0 50.50.13.1 0 50 30 200 ?
* 200.20.50.0 50.50.13.1 0 50 30 200 ?
* 200.20.60.0 50.50.13.1 0 50 30 200 ?

Total number of prefixes 9

R5_AS_192#sho ip bgp neighbors 60.50.10.5 routes
BGP table version is 33, local router ID is 192.168.10.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
*> 100.100.11.0/24 60.50.10.5 0 100 ?
*> 100.100.12.0/24 60.50.10.5 0 0 100 ?
*> 200.20.20.0 60.50.10.5 0 100 200 i
*> 200.20.30.0 60.50.10.5 0 100 200 ?
*> 200.20.40.0 60.50.10.5 0 100 200 ?
*> 200.20.50.0 60.50.10.5 0 100 200 ?
*> 200.20.60.0 60.50.10.5 0 100 200 ?

Total number of prefixes 7

R5_AS_192#sho ip ro bgp
50.0.0.0/8 is variably subnetted, 4 subnets, 3 masks
B 50.50.11.0/24 [20/0] via 50.50.13.1, 01:13:34
B 50.50.12.0/24 [20/0] via 50.50.13.1, 01:13:34
B 200.20.20.0/24 [20/0] via 60.50.10.5, 01:06:03
100.0.0.0/24 is subnetted, 2 subnets
B 100.100.11.0 [20/0] via 60.50.10.5, 01:06:59
B 100.100.12.0 [20/0] via 60.50.10.5, 01:06:59
B 200.20.50.0/24 [20/0] via 60.50.10.5, 01:06:03
B 200.20.60.0/24 [20/0] via 60.50.10.5, 01:06:03
B 200.20.30.0/24 [20/0] via 60.50.10.5, 01:06:03
B 200.20.40.0/24 [20/0] via 60.50.10.5, 01:06:03
30.0.0.0/24 is subnetted, 2 subnets
B 30.30.11.0 [20/0] via 50.50.13.1, 01:13:34
B 30.30.12.0 [20/0] via 50.50.13.1, 01:13:34

*** R5 is also getting two advertisement for the network 200.20.0.0 from R4 and R7 and again R7 advertisements gets to R5 routing table simply because there is a shorter path via R7.

R5_AS_192#sho ip bgp neighbors 60.50.10.5 advertised-routes
BGP table version is 33, local router ID is 192.168.10.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
*> 192.168.10.0 0.0.0.0 0 32768 i
*> 192.168.20.0 0.0.0.0 0 32768 ?
*> 192.168.30.0 0.0.0.0 0 32768 ?
*> 192.168.40.0 0.0.0.0 0 32768 ?
*> 192.168.50.0 0.0.0.0 0 32768 ?


R5_AS_192#sho ip bgp neighbors 50.50.13.1 advertised-routes
BGP table version is 33, local router ID is 192.168.10.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
*> 192.168.10.0 0.0.0.0 0 32768 i
*> 192.168.20.0 0.0.0.0 0 32768 ?
*> 192.168.30.0 0.0.0.0 0 32768 ?
*> 192.168.40.0 0.0.0.0 0 32768 ?
*> 192.168.50.0 0.0.0.0 0 32768 ?

*** R5 is advertising its networks to both of its peers

R5_AS_192#ping ip 200.20.20.1 so 192.168.10.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 200.20.20.1, timeout is 2 seconds:
Packet sent with a source address of 192.168.10.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 288/356/528 ms

R5_AS_192#traceroute ip

Target IP address: 200.20.20.1
Source address: 192.168.10.1
Numeric display [n]:
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Port Number [33434]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Type escape sequence to abort.
Tracing the route to 200.20.20.1

1 60.50.10.5 116 msec 72 msec 120 msec --> ISP AS 100
2 100.100.10.1 240 msec 408 msec 216 msec
3 60.50.10.2 288 msec * 288 msec

*** Connectivity tests: ping and traceroutes to R0

*** Next post are some tips and tricks that may be useful.