1 2 Previous Next 16 Replies Latest reply: Jun 12, 2019 1:09 AM by Francesco RSS

    BGP neighbor next-hop-self does not work !!

    mohammed

      hi,

       

      I am using CSR 1000v 9.03,

       

      I tried to do this on many routers and did not work on all, simply the iBGP routers still receive the original IP originator (of remote AS).

       

      I anticipate the issue in the CSR !!

       

      did anyone face this issue ?

        • 1. Re: BGP neighbor next-hop-self does not work !!
          Elvin Arias

          I'm using the CSR 1000v and I'm able to do that configuration successfully.

           

          Elvin

          • 2. Re: BGP neighbor next-hop-self does not work !!
            Murad

            Hi Mohammad,

             

            bgp next hop self is like a million years old option :-) and it should work like a charm. You might be having something wrong with the config.

             

            Please double check the configuration or publish it here so that can we can assist you.

             

            /Murad

            • 3. Re: BGP neighbor next-hop-self does not work !!
              Martin

              seen it working in videos ..do not use crs1000v

              • 4. Re: BGP neighbor next-hop-self does not work !!
                arteq

                just advertise the networks... (not a fan of next-hop-smellf)

                • 5. Re: BGP neighbor next-hop-self does not work !!
                  Murad

                  I ask you again, please publish topology and configuration to find the problem?

                  • 6. Re: BGP neighbor next-hop-self does not work !!
                    mohammed

                    Hi,

                     

                    please see this:

                     

                     

                    1.jpg

                     

                    I have shutdown link between R16 and R9.

                    so, R8 advertise network 8.8.8.8/32 through BGP

                     

                    R15 learns this prefix from eBGP toward R8 and then advertises it to R16. (next-hop-self is inserted on R15).

                    but R16 still learn prefix from R8 address (150.1.8.8). and it does not install it in the routing table because it does not have route to 150.1.8.8.

                     

                     

                    see configs:

                     

                    R15#show ip bgp         

                    BGP table version is 30, local router ID is 150.1.15.15

                     

                         Network          Next Hop            Metric LocPrf Weight Path

                    *>  1.1.1.1/32       150.1.1.1                0             0 4500 i

                    *>  8.8.8.8/32       150.1.8.8                0             0 3500 i

                    *                            150.1.1.1                              0 4500 3500 i

                     

                     

                     

                    R16#show ip bgp

                     

                         Network          Next Hop            Metric LocPrf Weight Path

                    * i 8.8.8.8/32       150.1.8.8                0    100      0 3500 i

                     

                     

                    R15#show run | s router bgp

                    neighbor 150.1.8.8 remote-as 3500

                    neighbor 150.1.8.8 ebgp-multihop 2

                    neighbor 150.1.8.8 update-source Loopback0

                    neighbor 150.1.8.8 next-hop-self

                     

                     

                    R15#show ip route 8.8.8.8

                    Routing entry for 8.8.8.8/32

                      Known via "bgp 5500", distance 20, metric 0

                      Tag 3500, type external

                      Advertised by bgp 5500 (self originated)

                      Last update from 150.1.8.8 00:53:20 ago

                      Routing Descriptor Blocks:

                      * 150.1.8.8, from 150.1.8.8, 00:53:20 ago

                          Route metric is 0, traffic share count is 1

                          AS Hops 1

                          Route tag 3500

                          MPLS label: none

                     

                     

                    R16#show ip route 8.8.8.8

                    % Network not in table

                     

                     

                     

                    this issue I have it on all routers configured with next-hop-self command. I do not think there is an issue in the config because it is straight forward.

                    • 7. Re: BGP neighbor next-hop-self does not work !!
                      Murad

                      You don't have IBGP neighbor in configuration for R16 in R15. You have configured next-hop-self towards R8 which is EBGP.You dont need it there. check your configuration and fix it.


                      Thanks

                      • 8. Re: BGP neighbor next-hop-self does not work !!
                        Murad

                        I would highly recommend to the read the following book to have a good understanding of BGP:

                         

                        Internet Routing Architectures, 2nd Edition

                         

                        /Murad

                        • 9. Re: BGP neighbor next-hop-self does not work !!
                          mohammed

                          sorry, I just omitted some outputs because they are a lot.

                           

                          R15#show ip bgp sum

                           

                          Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd

                          150.1.1.1       4         4500     484     494       30    0    0 07:12:15        5

                          150.1.8.8       4         3500     400     407       30    0    0 05:58:36        2

                          150.1.16.16     4         5500     463     461       30    0    0 06:48:18        8

                          R15#

                          • 10. Re: BGP neighbor next-hop-self does not work !!
                            Kevin Santillan

                            Mohammed,

                             

                            The next-hop-self command should be applied towards R16 and not R8 just like what Murad mentioned. The reason why R16 can't install 8.8.8.8 in its RIB is because can't recurse it to a valid next-hop since it does not know about 150.1.8.8. Apply the next-hop-self command towards R16 instead and things should work as you expect them to.

                            • 11. Re: BGP neighbor next-hop-self does not work !!
                              Murad

                              Mohammad,

                               

                              Copy paste below config in R15: then run show commands :-)

                               

                              conf t

                               

                              router bgp 5500

                               

                              neighbor 150.1.8.8 remote-as 3500

                               

                              neighbor 150.1.8.8 ebgp-multihop 2

                               

                              neighbor 150.1.8.8 update-source Loopback0

                               

                              no neighbor 150.1.8.8 next-hop-self

                               

                              neighbor 150.1.16.16 remote-as 5500

                               

                              neighbor 150.1.16.16 update-source Loopback0

                               

                              neighbor 150.1.16.16 next-hop-self

                               

                              end

                               

                              clear ip bgp *

                              • 12. Re: BGP neighbor next-hop-self does not work !!
                                mohammed

                                hi, thanks now it worked,

                                 

                                R16#show ip bgp

                                BGP table version is 12, local router ID is 150.1.16.16

                                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 1.1.1.1/32      150.1.15.15              0    100      0 4500 i

                                *>i 8.8.8.8/32      150.1.15.15              0    100      0 3500 i

                                 

                                 

                                so next-hop-self, should be inserted toward iBGP peers !! I thought it should be toward eBGP.

                                I was confused then about it.

                                 

                                 

                                thanks again.

                                • 13. Re: BGP neighbor next-hop-self does not work !!
                                  Murad

                                  In eBGP you don't need next-hop-self to configure.

                                   

                                  Plz remember to mark a question answered correct so that others can benefit from it.

                                   

                                  Thanks

                                  • 14. Re: BGP neighbor next-hop-self does not work !!
                                    Mark Holm - 3xCCIE #34763/CCDE #20160020

                                    Hi Mohammed,

                                     

                                    iBGP does not change the next-hop attribute as it assumes that your IGP will know about the associated next-hop. An eBGP peering will by default change the next-hop attribute to the local address associated with the eBGP peering under the assumption that IGP information is not shared between AS'es, so it uses an address that is common to/known by both AS'es as the next-hop.

                                     

                                    /Mark

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