eBGP configuration not populating routing table with learned routes #10067

davehouser1 · 2021-11-15T17:23:45Z

davehouser1
Nov 15, 2021

First of all, I am still learning the BGP protocol (hence why I deployed FRR)

Problem:
FRR is not populating the vtysh routing table or kernel routing table with learned bgp routes.

Topology:

                            CiscoIOSL3 (ASN 65101) Hostname: CiscoiouL3-4
                                                 |                 
                                                 |
                            CiscoIOSL3 (ASN 65102) Hostname: CiscoiouL3-5
                                                 |                 
                                                 |
                              Centos w/FRR (ASN 65103) Hostname: gst-3

Environment:

Running all in GNS3 2.2.22
FRR version 8.1

Configuration:
Here is my configuration for each system

CiscoIOSL3 (ASN 65101):

CiscoiouL3-4(config-router)#do show run
Building configuration...

Current configuration : 1585 bytes
!
version 15.7
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname CiscoiouL3-4
!
boot-start-marker
boot-end-marker
!
!
!
no aaa new-model
!
!
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
!
!
!
!
!
no ip icmp rate-limit unreachable
!
!
!
!
!
!
!
!
!
!


!
!
!
!
no ip domain lookup
ip cef
no ipv6 cef
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
!
redundancy
!
no cdp log mismatch duplex
!
ip tcp synwait-time 5
!
!
!
!
!
!
!
!
!
!
!
!
!
interface Ethernet0/0
 ip address 4.4.0.1 255.255.255.252
 duplex auto
!
interface Ethernet0/1
 ip address 4.4.1.1 255.255.255.252
 duplex auto
!
interface Ethernet0/2
 ip address 10.0.26.1 255.255.255.0
 duplex auto
!
interface Ethernet0/3
 no ip address
 duplex auto
!
interface Serial1/0
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial1/1
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial1/2
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial1/3
 no ip address
 shutdown
 serial restart-delay 0
!
router bgp 65101
 bgp router-id 4.4.0.1
 bgp log-neighbor-changes
 redistribute connected
 neighbor 4.4.0.2 remote-as 65102
!
ip forward-protocol nd
!
!
no ip http server
no ip http secure-server
!
ipv6 ioam timestamp
!
!
!
control-plane
!
!
!
!
!
!
!
!
line con 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line aux 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line vty 0 4
 login
 transport input none
!
!
end

CiscoIOSL3 (ASN 65102)

Building configuration...

Current configuration : 1626 bytes
!
! Last configuration change at 16:01:26 UTC Mon Nov 15 2021
!
version 15.7
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname CiscoiouL3-5
!
boot-start-marker
boot-end-marker
!
!
!
no aaa new-model
!
!
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
!
!
!
!
!
no ip icmp rate-limit unreachable
!
!
!
!
!
!
!
!
!
!


!
!
!
!
no ip domain lookup
ip cef
no ipv6 cef
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
!
redundancy
!
no cdp log mismatch duplex
!
ip tcp synwait-time 5
!
!
!
!
!
!
!
!
!
!
!
!
!
interface Ethernet0/0
 ip address 4.4.0.2 255.255.255.252
 duplex auto
!
interface Ethernet0/1
 ip address 3.3.0.1 255.255.255.252
 duplex auto
!
interface Ethernet0/2
 no ip address
 duplex auto
!
interface Ethernet0/3
 no ip address
 duplex auto
!
interface Serial1/0
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial1/1
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial1/2
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial1/3
 no ip address
 shutdown
 serial restart-delay 0
!
router bgp 65102
 bgp router-id 3.3.0.1
 bgp log-neighbor-changes
 redistribute connected
 neighbor 3.3.0.2 remote-as 65103
 neighbor 4.4.0.1 remote-as 65101
!
ip forward-protocol nd
!
!
no ip http server
no ip http secure-server
!
ipv6 ioam timestamp
!
!
!
control-plane
!
!
!
!
!
!
!
!
line con 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line aux 0
 exec-timeout 0 0
 privilege level 15
 logging synchronous
line vty 0 4
 login
 transport input none
!
!
end

Centos w/FRR (ANS 65103)

Building configuration...

Current configuration:
!
frr version 8.1
frr defaults traditional
hostname gst-3
log syslog informational
no ipv6 forwarding
service integrated-vtysh-config
!
debug bgp neighbor-events
!
interface LoopBack0
 ip address 1.2.3.4/24
exit
!
router bgp 65103
 bgp router-id 3.3.0.2
 bgp log-neighbor-changes
 no bgp ebgp-requires-policy
 neighbor 3.3.0.1 remote-as 65102
 neighbor 3.3.0.1 disable-connected-check
 !
 address-family ipv4 unicast
  redistribute connected
  neighbor 3.3.0.1 soft-reconfiguration inbound
 exit-address-family
exit
!
end

BGP status

CiscoIOSL3 (ASN 65101)

CiscoiouL3-4(config)#do show ip route
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

      3.0.0.0/30 is subnetted, 1 subnets
B        3.3.0.0 [20/0] via 4.4.0.2, 01:02:21
      4.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C        4.4.0.0/30 is directly connected, Ethernet0/0
L        4.4.0.1/32 is directly connected, Ethernet0/0
C        4.4.1.0/30 is directly connected, Ethernet0/1
L        4.4.1.1/32 is directly connected, Ethernet0/1
      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        10.0.26.0/24 is directly connected, Ethernet0/2
L        10.0.26.1/32 is directly connected, Ethernet0/2

CiscoiouL3-4(config)#do show bgp all
For address family: IPv4 Unicast

BGP table version is 34, local router ID is 4.4.0.1
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,
              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
 *>   3.3.0.0/30       4.4.0.2                  0             0 65102 ?
 *    4.4.0.0/30       4.4.0.2                  0             0 65102 ?
 *>                    0.0.0.0                  0         32768 ?
 *>   4.4.1.0/30       0.0.0.0                  0         32768 ?
 *>   10.0.26.0/24     0.0.0.0                  0         32768 ?

For address family: IPv4 Multicast


For address family: L2VPN E-VPN


For address family: MVPNv4 Unicast

CiscoIOSL3 (ASN 65102)

CiscoiouL3-5(config)#do show ip route
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

      3.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        3.3.0.0/30 is directly connected, Ethernet0/1
L        3.3.0.1/32 is directly connected, Ethernet0/1
      4.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
C        4.4.0.0/30 is directly connected, Ethernet0/0
L        4.4.0.2/32 is directly connected, Ethernet0/0
B        4.4.1.0/30 [20/0] via 4.4.0.1, 01:02:08
      10.0.0.0/24 is subnetted, 1 subnets
B        10.0.26.0 [20/0] via 4.4.0.1, 01:02:08

CiscoiouL3-5(config)#do show bgp all
For address family: IPv4 Unicast

BGP table version is 11, local router ID is 3.3.0.1
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,
              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
 *>   3.3.0.0/30       0.0.0.0                  0         32768 ?
 *    4.4.0.0/30       4.4.0.1                  0             0 65101 ?
 *>                    0.0.0.0                  0         32768 ?
 *>   4.4.1.0/30       4.4.0.1                  0             0 65101 ?
 *>   10.0.26.0/24     4.4.0.1                  0             0 65101 ?

For address family: IPv4 Multicast


For address family: L2VPN E-VPN


For address family: MVPNv4 Unicast

Centos w/FRR (ASN 65103)

gst-3(config)# do show ip bgp neighbors 3.3.0.1 received-routes
BGP table version is 4, local router ID is 3.3.0.2, vrf id 0
Default local pref 100, local AS 65103
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

   Network          Next Hop            Metric LocPrf Weight Path
*> 3.3.0.0/30       3.3.0.1                  0             0 65102 ?
*> 4.4.0.0/30       3.3.0.1                  0             0 65102 ?
*> 4.4.1.0/30       3.3.0.1                                0 65102 65101 ?
*> 10.0.26.0/24     3.3.0.1                                0 65102 65101 ?

Total number of prefixes 4

gst-3(config)# do show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, A - Babel, F - PBR, f - OpenFabric,
       > - selected route, * - FIB route, q - queued, r - rejected, b - backup
       t - trapped, o - offload failure

C>* 3.3.0.0/30 is directly connected, ens4, 01:16:52
K>* 10.212.134.0/24 [0/100] via 192.168.0.1, ens3, 1d21h34m
C>* 192.168.0.0/24 is directly connected, ens3, 1d21h34m

I also did a TCPdump on the centos box, and see packets coming to port 179 and the advertised networks inside of them. I want to make sure all hosts are only using eBGP and not iBGP (avoid split horizon). I believe this is just a configuration issue. I tried reading though the documentation here , however for someone that is still learning BGP, the number of configurations you can use is like drinking from a firehose. Is there some place that shows basic examples of how to configure eBGP in a full mesh?

Is my FRR configuration incorrect? If show how can I fix it?

davehouser1 · 2021-11-15T19:45:00Z

davehouser1
Nov 15, 2021
Author

Think I figured it out, however not sure I understand.
I found this link .
I set zebra=yes and restarted the frr service, and then routes appeared in the vtysh table and the kernel table!
What is odd though is, I had some ibgp configurations in place prior to my problem, and the vtysh routing table and kernel routing table was populating just fine. Not sure I understand why it would have stopped working, and I would need to enable zebra. Is zebra enabled by default on frr 8.1?

Its working right now how before I set this as the answered question was wondering if anyone could share their thoughts only why my routing tables were populating, then it stopped?

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eBGP configuration not populating routing table with learned routes #10067

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eBGP configuration not populating routing table with learned routes #10067

davehouser1 Nov 15, 2021

Replies: 1 comment

davehouser1 Nov 15, 2021 Author

davehouser1
Nov 15, 2021

davehouser1
Nov 15, 2021
Author