Initial configuration
on each routers. As below:
R1#sh ip int br | e
una
Interface IP-Address OK? Method Status Protocol
Serial1/0 11.0.0.2 YES manual up up
Serial1/1 11.0.0.6 YES manual up up
Serial1/2 10.0.0.1 YES manual up up
Loopback0 1.1.1.1 YES manual up up
R2#sh ip int br | e
una
Interface IP-Address OK? Method Status Protocol
Serial1/0 10.0.0.2 YES manual up up
Serial1/1 10.0.0.5 YES manual up up
Loopback0 2.2.2.2 YES manual up up
R3#sh ip int br | e
una
Interface IP-Address OK? Method Status Protocol
Serial1/0 10.0.0.6 YES manual up up
Serial1/1 10.0.0.9 YES manual up up
Loopback0 3.3.3.3 YES manual up up
R4#sh ip int br | e
una
Interface IP-Address OK? Method Status Protocol
Serial1/0 10.0.0.10 YES manual up up
Serial1/1 11.0.0.9 YES manual up up
Serial1/2 11.0.0.13 YES manual up up
Loopback0 4.4.4.4 YES manual up up
R5#sh ip int b | e
una
Interface IP-Address OK? Method Status Protocol
Serial1/0 11.0.0.10 YES manual up up
Loopback0 50.0.0.1 YES manual up up
Loopback1 50.1.1.1 YES manual up up
Loopback2 50.2.2.1 YES manual up up
R6#sh ip int b | e
una
Interface IP-Address OK? Method Status Protocol
Serial1/0 11.0.0.14 YES manual up up
Loopback0 60.0.0.1 YES manual up up
Loopback1 60.1.1.1 YES manual up up
Loopback2 60.2.2.1 YES manual up up
R7#sh ip int b | e
una
Interface IP-Address OK? Method Status Protocol
Serial1/0 11.0.0.1 YES manual up up
Loopback0 70.0.0.1 YES manual up up
Loopback1 70.1.1.1 YES manual up up
Loopback2 70.2.2.1 YES manual up up
R8#sh ip int b | e
una
Interface IP-Address OK? Method Status Protocol
Serial1/0 11.0.0.5 YES manual up up
Loopback0 80.0.0.1 YES manual up up
Loopback1 80.1.1.1 YES manual up up
Loopback2 80.2.2.1 YES manual up up
Here as shown in
the figure I have created a VRF and MP-BGP.
Now am going to run
BGP as PE-CE routing.
R1(config)#router
bgp 100
R1(config-router)#address-family
ipv4 vrf A
R1(config-router-af)#neighbor
11.0.0.5 remote-as 65031
R7(config)#router
bgp 65031
R7(config-router)#neighbor
11.0.0.6 remote-as 100
R7(config-router)#network
70.0.0.0 mask 255.255.255.0
Now check the bgp
peer state.
R7#sh ip bgp su |
be Ne
Neighbor V
AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
11.0.0.6 4
100 11 12
2 0 0 00:07:19 0
R1#sh ip bgp vpnv4
vrf A summary | be Ne
Neighbor V
AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
11.0.0.5 4 65031 13
12 2 0
0 00:08:02 1
As we know 70.0.0.0/24
network we published in BGP R1 receiving it. In BGP we don’t need to
redistribute the VPNv4 prefix into BGP since it’s a automatic process.
Therefore lets
check o R4.
R4#sh ip bgp vpnv4
vrf A
BGP table version
is 3, local router ID is 4.4.4.4
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
Route
Distinguisher: 500:5 (default for vrf A)
*>i70.0.0.0/24 1.1.1.1 0 100
0 65031 i
Ahhh as we guessed
we are getting the prefix now lets run BGP between PE-CE router.
R4(config)#router
bgp 100
R4(config-router)#address-family
ipv4 vrf A
R4(config-router-af)#neighbor
11.0.0.10 remote-as 65031
R5(config)#router
bgp 65031
R5(config-router)#neighbor
11.0.0.9 remot 100
Lets check the BGP
neighborship
R5#sh ip bgp su |
be Ne
Neighbor V
AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
11.0.0.9 4
100 5 4
1 0 0 00:00:55 0
Cool we formed
neighborship between PE-CE routers. Now lets check for the prefix 70.0.0.0/24
R5#sh ip route
70.0.0.0
% Network not in table
R5#sh ip bgp
R5#
Strange we are not
getting the prefix but on R4 we have the prefix.
Lets run the debug
R5#debug ip bgp
ipv4 unicast updates in
BGP updates debugging
is on (inbound) for address family: IPv4 Unicast
BGP(0): 11.0.0.9 rcv UPDATE w/ attr: nexthop 11.0.0.9,
origin i, originator 0.0.0.0, path 100 65031, community , extended community
BGP(0): 11.0.0.9 rcv UPDATE about 70.0.0.0/24 --
DENIED due to: AS-PATH contains our own AS;
See, Yes BGP
AS-Path attribute detecting the LOOP and R5 not installing the prefix. To overcome
this problem we have two options
Option 1:
Allow As-in
R5(config)#router
bgp 65031
R5(config-router)#neighbor
11.0.0.9 allowas-in ?
<1-10>
Number of occurances of AS number
<cr>
R5(config-router)#neighbor
11.0.0.9 allowas-in 1
R5#sh ip route bgp
70.0.0.0/24 is subnetted, 1 subnets
B 70.0.0.0 [20/0] via 11.0.0.9, 00:00:31
R5#sh ip bgp
BGP table version
is 2, local router ID is 50.2.2.1
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
*>
70.0.0.0/24 11.0.0.9 0 100 65031 i
Option 2:
Autonomous System Override
To work on this am
going to publish the network 50.0.0.0/24 in BGP on R5.
R5(config)#router
bgp 65031
R5(config-router)#network
50.0.0.0 mask 255.255.255.0
R1#sh ip bgp vpnv4
vrf A
BGP table version
is 4, 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
Origin codes: i - IGP,
e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route
Distinguisher: 700:7 (default for vrf A)
*>i50.0.0.0/24 4.4.4.4 0 100
0 65031 i
*>
70.0.0.0/24 11.0.0.5 0
0 65031 i
R1#
So prefix reached
till R1 as we already aware of this problem that R7 will not take this prefix
as AS-Path loop. Lets check and confirm it.
R7#sh ip route bgp
R7#
R1(config)#router
bgp 100
R1(config-router)#address-family
ipv4 vrf A
R1(config-router-af)#neighbor
11.0.0.5 as-override
R7#sh ip route bgp
50.0.0.0/24 is subnetted, 1 subnets
B 50.0.0.0 [20/0] via 11.0.0.6, 00:01:25
R7#sh ip bgp
BGP table version
is 3, local router ID is 70.2.2.1
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
*> 50.0.0.0/24
11.0.0.6
0 100 100 i
*>
70.0.0.0/24 0.0.0.0 0 32768 i
Note: This command
will work on PE and see the AS path its duplicated with the SP AS num.
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