EBGP not have advertises network to ibgp

donho1987 · October 12, 2022, 5:23am

I try to setup a control panel for BGP 300 and the data plane with private BGP 70000, i have ar01 configured as a router reflector, pr01 as a client, and net-hop-self to ar01 device, i configure is-is from ar01 to csw router.
The Csw, ASW router is not advertising the network 192.168.3.0, but it configures IBGP on the neighbor interface only,

ar01 can ping loop 3.3.3.3
csw can ping loop 1.1.1.1

I question how to conf on pr01 and csw to make asw1 and ar01 ping their loop back. And able to advertise all routes to peer network

lagapidis · October 14, 2022, 4:56am

Hello Duong

Here are a few of my concerns with what you’ve described.

You say you’ve set next-hop-self on the AR01 device. Ideally, this should be configured on the device with the eBGP peering, which is the PR01 device. Otherwise, when PR01 advertises the 1.1.1.1/32 network to BGP 70000, it will give a next hop IP of 192.168.1.1 which is that of AR01. But that address is not reachable from the other ASes. Take a look at the BGP Next Hop Self lesson for more information on how that works.
You say you have configured IS-IS from AR01 to CSW. This is an unorthodox approach, as you are running an IGP from one AS to another. In order to avoid unpredictable routing, it is best practice to keep IGPs within ASes, and have only eBGP share routes between ASes.
You’re using an ASN of 70000 for one of the ASes. This is a 32-bit ASN since it is larger than 65535. Make sure all of your devices support 32-bit ASNs, otherwise the topology won’t work.
I’m not sure what role the green Peer network router is playing, but since you don’t mention it, I assume it is not involved.

My suggestion would be to do the following:

Ensure that your IGP is running only within each AS
Make sure BGP is configured to advertise all the prefixes correctly
Make sure that the prefixes being advertised are found within the routing tables of the local routers. This is a prerequisite for advertising a BGP route.
Make sure the next hop self feature is configured on the eBGP router that connects to another AS. In your case, it should be configured on the csw and the pr01 routers so that they advertise themselves as the next hop for all prefixes of their AS.

Take a look at the following two lessons that detail how to share routes between ASes.

I hope this has been helpful!

Laz

donho1987 · October 15, 2022, 1:00pm

My ar01 got next hop via IP to add 2.2.2.2. this bgp3000 in a roll control plane and bgp70000 in a data plane, Peernetwork, as costumer ixp, i do configure pr01 next-hop-self toward ar01.01, no next hop seft on ar01. The is-is from ar01 to csw is acceptable because BGP 70000 is my private AS, i have seen this configure in a production network. My, configure bellow.

ar01#show running-config | begin isis
 ip router isis 
!
interface Ethernet0/0
 description et-0-0:pr01
 ip address 192.168.1.1 255.255.255.252
 ip router isis 
 duplex auto
!

router isis
 net 49.0001.0010.0100.1001.00
 log-adjacency-changes

router bgp 3000
 bgp log-neighbor-changes
 network 1.1.1.1 mask 255.255.255.255
 neighbor 2.2.2.2 remote-as 3000
 neighbor 2.2.2.2 update-source Loopback0
 neighbor 2.2.2.2 route-reflector-client

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
2.2.2.2         4         3000       2       2        1    0    0 00:00:00        0sho


     Network          Next Hop            Metric LocPrf Weight Path
 *>   1.1.1.1/32       0.0.0.0                  0         32768 i
 r>i  2.2.2.2/32       2.2.2.2                  0    100      0 i
 r>i  3.3.3.3/32       2.2.2.2                  0    100      0 70000 i
 *>i  4.4.4.4/32       2.2.2.2                  0    100      0 70000 i
 *>i  5.5.5.5/32       2.2.2.2                  0    100      0 70000 i

ar01#show ip route bgp
Codes: L - local, 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, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      4.0.0.0/32 is subnetted, 1 subnets
B        4.4.4.4 [200/0] via 2.2.2.2, 00:01:08
      5.0.0.0/32 is subnetted, 1 subnets
B        5.5.5.5 [200/0] via 2.2.2.2, 00:01:08
ar01#

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

pr01#show running-config  | begin isis
 ip router isis 
!
interface Ethernet0/0
 description et-0-0:ar01
 ip address 192.168.1.2 255.255.255.252
 ip router isis 
 duplex auto
!
interface Ethernet0/1
 description et-0-0:csw1
 ip address 192.168.2.2 255.255.255.252
 ip router isis 
 duplex auto


 router isis
 net 49.0001.0020.0200.2002.00
 is-type level-1
!
router bgp 3000
 bgp log-neighbor-changes
 network 2.2.2.2 mask 255.255.255.255
 neighbor 1.1.1.1 remote-as 3000
 neighbor 1.1.1.1 update-source Loopback0
 neighbor 1.1.1.1 next-hop-self
 neighbor 172.10.10.1 remote-as 4000
 neighbor 172.10.10.1 description Peer-as4000:u=CID-ABC:I=CID-netwokr:BE2
 neighbor 192.168.2.1 remote-as 70000


Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
1.1.1.1         4         3000       9      11        6    0    0 00:05:14        1
172.10.10.1     4         4000       2       9        6    0    0 00:00:00        0
192.168.2.1     4        70000      10      10        6    0    0 00:05:13        3


Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 r>i  1.1.1.1/32       1.1.1.1                  0    100      0 i
 *>   2.2.2.2/32       0.0.0.0                  0         32768 i
 *>   3.3.3.3/32       192.168.2.1              0             0 70000 i
 *>   4.4.4.4/32       192.168.2.1                            0 70000 i
 *>   5.5.5.5/32       192.168.2.1                            0 70000 i
pr01# sho


pr01# show ip route bgp
Codes: L - local, 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, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      3.0.0.0/32 is subnetted, 1 subnets
B        3.3.3.3 [20/0] via 192.168.2.1, 00:04:53
      4.0.0.0/32 is subnetted, 1 subnets
B        4.4.4.4 [20/0] via 192.168.2.1, 00:04:53
      5.0.0.0/32 is subnetted, 1 subnets
B        5.5.5.5 [20/0] via 192.168.2.1, 00:04:53
pr01#

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

csw1#show running-config | begin isis
 ip router isis 
!
interface Ethernet0/0
 description et-0-0:asw1
 ip address 192.168.3.1 255.255.255.252
 duplex auto
!
interface Ethernet0/1
 description et-0-1:pr01
 ip address 192.168.2.1 255.255.255.252
 ip router isis 
 duplex auto


router isis
 net 49.0001.0030.0300.3003.00
 is-type level-1
!
router bgp 70000
 bgp log-neighbor-changes
 network 3.3.3.3 mask 255.255.255.255
 neighbor 192.168.2.2 remote-as 3000
 neighbor 192.168.3.2 remote-as 70000
 neighbor 192.168.3.2 next-hop-self
!

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/Pfx
Rcd
192.168.2.2     4         3000      13      13        8    0    0 00:07:17        4
192.168.3.2     4        70000      12      14        8    0    0 00:07:12        2 

Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>   1.1.1.1/32       192.168.2.2                            0 3000 i
 *>   2.2.2.2/32       192.168.2.2              0             0 3000 i
 *>   3.3.3.3/32       0.0.0.0                  0         32768 i
 *>i  4.4.4.4/32       192.168.3.2              0    100      0 i
 *>i  5.5.5.5/32       192.168.3.2              0    100      0 i
 *>   192.10.1.0/32    192.168.2.2                            0 3000 4000 i
 *>   192.10.2.0/32    192.168.2.2                            0 3000 4000 i
csw1#


csw1#show ip rou
csw1#show ip route bgp
Codes: L - local, 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, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      1.0.0.0/32 is subnetted, 1 subnets
B        1.1.1.1 [20/0] via 192.168.2.2, 00:07:14
      2.0.0.0/32 is subnetted, 1 subnets
B        2.2.2.2 [20/0] via 192.168.2.2, 00:07:14
      4.0.0.0/32 is subnetted, 1 subnets
B        4.4.4.4 [200/0] via 192.168.3.2, 00:07:22
      5.0.0.0/32 is subnetted, 1 subnets
B        5.5.5.5 [200/0] via 192.168.3.2, 00:07:22
      192.10.1.0/32 is subnetted, 1 subnets
B        192.10.1.0 [20/0] via 192.168.2.2, 00:02:13
      192.10.2.0/32 is subnetted, 1 subnets
B        192.10.2.0 [20/0] via 192.168.2.2, 00:02:13
csw1#

============================================================================
asw

interface Loopback0
 ip address 4.4.4.4 255.255.255.255
!
interface Loopback1
 ip address 5.5.5.5 255.255.255.255
!
interface Ethernet0/0
 description e-0-0:csw1
 ip address 192.168.3.2 255.255.255.252
 duplex auto

!
router bgp 70000
 bgp log-neighbor-changes
 network 4.4.4.4 mask 255.255.255.255
 network 5.5.5.5 mask 255.255.255.255
 neighbor 192.168.3.1 remote-as 70000

show io  
asw1# 

asw1#show ip bgp sum
asw1#show ip bgp summary 
BGP router identifier 5.5.5.5, local AS number 70000
BGP table version is 8, main routing table version 8
7 network entries using 1008 bytes of memory
7 path entries using 588 bytes of memory
4/4 BGP path/bestpath attribute entries using 640 bytes of memory
2 BGP AS-PATH entries using 48 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 2284 total bytes of memory
BGP activity 7/0 prefixes, 7/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.3.1     4        70000      20      18        8    0    0 00:13:11        5
asw1#show ip bgp
BGP table version is 8, local router ID is 5.5.5.5
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, 
              t secondary path, 
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  1.1.1.1/32       192.168.3.1              0    100      0 3000 i
 *>i  2.2.2.2/32       192.168.3.1              0    100      0 3000 i
 *>i  3.3.3.3/32       192.168.3.1              0    100      0 i
 *>   4.4.4.4/32       0.0.0.0                  0         32768 i
 *>   5.5.5.5/32       0.0.0.0                  0         32768 i
 *>i  192.10.1.0/32    192.168.3.1              0    100      0 3000 4000 i
 *>i  192.10.2.0/32    192.168.3.1              0    100      0 3000 4000 i
asw1#show ip rou
asw1#show ip route bgp
Codes: L - local, 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, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      1.0.0.0/32 is subnetted, 1 subnets
B        1.1.1.1 [200/0] via 192.168.3.1, 00:12:20
      2.0.0.0/32 is subnetted, 1 subnets
B        2.2.2.2 [200/0] via 192.168.3.1, 00:12:20
      3.0.0.0/32 is subnetted, 1 subnets
B        3.3.3.3 [200/0] via 192.168.3.1, 00:12:28
      192.10.1.0/32 is subnetted, 1 subnets
B        192.10.1.0 [200/0] via 192.168.3.1, 00:07:19
      192.10.2.0/32 is subnetted, 1 subnets
B        192.10.2.0 [200/0] via 192.168.3.1, 00:07:19
asw1#

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

BGP router identifier 192.10.2.0, local AS number 4000
BGP table version is 8, main routing table version 8
7 network entries using 1008 bytes of memory
7 path entries using 588 bytes of memory
4/4 BGP path/bestpath attribute entries using 640 bytes of memory
2 BGP AS-PATH entries using 48 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 2284 total bytes of memory
BGP activity 7/0 prefixes, 7/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/Pfx
Rcd
172.10.10.2     4         3000      17      11        8    0    0 00:06:54        5
Peernetwork#show rou
Peernetwork#show ip rou
Peernetwork#show ip route bgp
Codes: L - local, 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, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      1.0.0.0/32 is subnetted, 1 subnets
B        1.1.1.1 [20/0] via 172.10.10.2, 00:06:06
      2.0.0.0/32 is subnetted, 1 subnets
B        2.2.2.2 [20/0] via 172.10.10.2, 00:06:06
      3.0.0.0/32 is subnetted, 1 subnets
B        3.3.3.3 [20/0] via 172.10.10.2, 00:06:06
      4.0.0.0/32 is subnetted, 1 subnets
B        4.4.4.4 [20/0] via 172.10.10.2, 00:06:06
      5.0.0.0/32 is subnetted, 1 subnets
B        5.5.5.5 [20/0] via 172.10.10.2, 00:06:06
Peernetwork#

lagapidis · October 19, 2022, 10:54am

Hello again Duong

Going back to your original question, in order to get this up and running you must ensure that:

ASW1 has in its IGP routing table a route to CSW.
ASW1 must have an iBGP peering with CSW
CSW must have a successful eBGP peering with PR01
PR01 must have a successful iBGP peering with AR01
CSW must advertise 1.1.1.1/32 that it learns from PR01 to ASW1 with itself as the next hop IP.
Similarly, PR01 must advertise 5.5.5.5/32 that it learns from CSW to AR01 with itself as the next hop IP

In your troubleshooting process, you should check to see within each AS, what prefixes appear in the IGP routing table and what prefixes appear in the BGP table. Once you find a prefix that is missing from a particular table, you can then troubleshoot that specific advertisement.

Let us know how you get along!

I hope this has been helpful!

Laz

donho1987 · October 19, 2022, 11:44pm

Hello Lagapides

Thank you for your help going to steps 1 to 6; I’m very sure that steps 1 to 4 it good; the problem is i don’t know how to conf advertise on csw and pr01.

but i checked again today i did not change anything configured i can ping using the source IP
any idea why

 ar01#ping 5.5.5.5 source 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/2 ms
ar01#ping 5.5.5.5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
ar01#

% Type "show ?" for a list of subcommands
asw1#ping 1.1.1.1 so
asw1#ping 1.1.1.1 source 5.5.5.5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
Packet sent with a source address of 5.5.5.5 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms
asw1#ping 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
...

lagapidis · October 21, 2022, 6:56am

Hello Duong

Ah yes, that makes perfect sense now. This is indeed normal behavior and I will explain.

When you don’t specify the source interface or source IP address of the ping, the source used is always the IP address of the exit interface indicated by the routing table for the particular destination being pinged. So when you ping 5.5.5.5 from AR01, you are using a source IP address of 192.168.1.1 which is the IP address of the exit interface e0/0. The echo request reaches ASW1, but ASW1 must now send a reply to 192.168.1.1. Does ASW1 know about the 192.168.1.0/31 network? No, so the echo reply fails. Something similar happens when you ping from ASW1 to 1.1.1.1.

However, when you use 1.1.1.1 as your source, when the ping reaches ASW1, it creates an echo reply with a destination of 1.1.1.1. It knows how to get to that destination, because it has learned about it from BGP, so the echo reply is successful.

Take a look at the NetworkLessons note on ping troubleshooting concepts for more info about this.

The good news is that your setup is working as expected, so you’re all set!

I hope this has been helpful!

Laz

donho1987 · October 22, 2022, 9:38pm

Hello Lagaoides

Thank you for your explanation. That is a perfect match sense, i will continue work on my lap, i may need to configure a VLAN on aws1, and i need to figure out how to give the peer network communication with that VLAN, but anyway, thank you for your help so much appreciate.