Vol.2 Lab.4 Ticket.4 - Solution Doesn't Entirely Work - Needs More Solution

Hi Folks,

In this trouble ticket, the solution guides says that SW4 isn't installing the BGP route because Synchronization is enabled and we don't have a corresponding route in the IGP. Make sense so I quickly check all the routers in the rest of the AS200 domain and notice they all have synchronization disabled. So I feel safe to disable the synchronization feature.

However, that didnt' allow the BGP prefix to get installed into the RIB. A quick 'debug bgp ipv4 unicast updates' reveals the following...

03:01:09: BGP(0): 40.1.2.2 rcvd UPDATE w/ attr: nexthop 40.1.2.2, origin ?, localpref 100, metric 4294967295, atomic-aggregate, aggregated by 100 40.1.5.5, path 100 11
03:01:09: BGP(0): 40.1.2.2 rcvd 40.1.0.0/21
03:01:09: BGP(0): no valid path for 40.1.0.0/21
03:01:09: BGP(0): nettable_walker 40.1.0.0/21 no best path
03:01:09: BGP(0): 40.1.106.6 send unreachable 40.1.0.0/21
03:01:09: BGP(0): 40.1.106.6 send UPDATE 40.1.0.0/21 -- unreachable

Rack1SW4(config-router)#
03:01:31: BGP(0): no valid path for 40.1.0.0/21

 

Let's check the BGP table....As we can see the metric is set to the maximum metric.

Paths: (2 available, no best path)
  Not advertised to any peer
  100 11, (aggregated by 100 40.1.5.5)
    40.1.2.2 (metric 2) from 40.1.2.2 (40.1.2.2)
      Origin incomplete, metric 4294967295, localpref 100, valid, internal, atomic-aggregate
  100 11, (aggregated by 100 40.1.3.3)
    40.1.4.4 (metric 1) from 40.1.4.4 (40.1.4.4)
      Origin incomplete, metric 4294967295, localpref 100, valid, internal, atomic-aggregate

 

So I ask myself? Does BGP not install routes that have maximum metric? I
don't seem to remember. I'll artificially set the metric lower as the BGP
update is recieved and see what happens...

 

ip prefix-list AS100_AGGREGATE seq 5 permit 40.1.0.0/21

route-map RMAP_SET_METRIC permit 10
 match ip address prefix-list AS100_AGGREGATE
 set metric 0
!
route-map RMAP_SET_METRIC permit 20

Rack1SW4(config-router)#neighbor 40.1.2.2 route-map RMAP_SET_METRIC in
Rack1SW4(config-router)#neighbor 40.1.4.4 route-map RMAP_SET_METRIC in

Rack1SW4(config-router)#do clear ip bgp * soft

...

BGP(0): 40.1.2.2 rcvd 40.1.0.0/21
BGP(0): Revise route installing 1 of 1 route for 40.1.0.0/21 -> 40.1.2.2 to main IP table

Rack1SW4(config-router)#do show ip bgp              
BGP table version is 85, local router ID is 40.1.10.10
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
...
* i40.1.0.0/21      40.1.2.2                      100      0 100 11 ?
*>i                 40.1.4.4                      100      0 100 11 ?

...

 

So we can see that the additional step was necessary i order to meet the requirements.

Mike

Comments

  • Paths: (2 available, no best path)
      Not advertised to any peer
      100 11, (aggregated by 100 40.1.5.5)
        40.1.2.2 (metric 2) from 40.1.2.2 (40.1.2.2)
          Origin incomplete, metric 4294967295, localpref 100, valid, internal, atomic-aggregate
      100 11, (aggregated by 100 40.1.3.3)
        40.1.4.4 (metric 1) from 40.1.4.4 (40.1.4.4)
          Origin incomplete, metric 4294967295, localpref 100, valid, internal, atomic-aggregate

    Hi Michael, just curious, where does the max metric come from?

  • My guess is on R3 and R5 both have the med configuration set:

    router bgp 100
     no synchronization
     bgp router-id 40.1.3.3
     bgp log-neighbor-changes
     bgp bestpath med missing-as-worst
     network 40.1.3.0 mask 255.255.255.0
     aggregate-address 40.1.0.0 255.255.248.0 as-set summary-only advertise-map ADVERTISE_MAP
     redistribute ospf 1
     neighbor 40.1.5.5 remote-as 100
     neighbor 40.1.5.5 update-source Loopback0
     neighbor 40.1.13.1 remote-as 11
     neighbor 40.1.23.2 remote-as 200
     neighbor 40.1.34.4 remote-as 200
     no auto-summary
    !

     

  • Hello Michael,

    I think the route-map to change the metric is not necessary. Actually I did this TS Lab yesterday and got my ass kicked but for ticket 4 I did exactly what the solution said and it worked but, only after doing "clear ip bgp *" and  "clear ip route *" and having a little patience. Of course, it's not something we would do on a production environment [;)]

    I'm afraid I have a loooooong log for this ticket, but I hope it helps. If you have time and tokens, let's try it:

     

    Rack10SW4#show ip bgp 40.10.0.0

    BGP routing table entry for 40.10.0.0/21, version 0

    Paths: (2 available, no best path)

      Not advertised to any peer

      100 11, (aggregated by 100 40.10.5.5)

        40.10.4.4 (metric 1) from 40.10.4.4 (40.10.4.4)

          Origin incomplete, metric 4294967295, localpref 100, valid, internal, not synchronized, atomic-aggregate

      100 11, (aggregated by 100 40.10.3.3)

        40.10.2.2 (metric 2) from 40.10.2.2 (40.10.2.2)

          Origin incomplete, metric 4294967295, localpref 100, valid, internal, not synchronized, atomic-aggregate

    Rack10SW4#

    Rack10SW4(config)#router bgp 200

    Rack10SW4(config-router)#no synchronization 

    Rack10SW4(config-router)#end

    Rack10SW4#

    Rack10SW4#

    *Mar  1 01:59:25.199: %SYS-5-CONFIG_I: Configured from console by console

    Rack10SW4#

    Rack10SW4#

    Rack10SW4#show ip bgp

    BGP table version is 33, local router ID is 40.10.10.10

    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

    * i28.119.16.0/24   40.10.8.8                0    100      0 100 54 i

    *>                  40.10.106.6                            0 100 54 i

    * i28.119.17.0/24   40.10.8.8                0    100      0 100 54 i

    *>                  40.10.106.6                            0 100 54 i

    * i40.10.0.0/21     40.10.4.4       4294967295    100      0 100 11 ?

    * i                 40.10.2.2       4294967295    100      0 100 11 ?

    r>i40.10.2.0/24     40.10.2.2                0    100      0 i

    r>i40.10.4.0/24     40.10.4.4                0    100      0 i

    * i40.10.6.0/24     40.10.8.8                0    100      0 100 i

    *>                  40.10.106.6              0             0 100 i

    r>i40.10.8.0/24     40.10.8.8                0    100      0 i

    * i40.10.9.0/24     40.10.2.2                2    100      0 100 ?

    * i                 40.10.4.4                2    100      0 100 ?

    *> 40.10.10.0/24    0.0.0.0                  0         32768 i

    * i40.10.13.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

    * i40.10.15.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

    r i40.10.23.0/24    40.10.2.2                0    100      0 100 ?

    r>i                 40.10.4.4                0    100      0 100 ?

     

    Rack10SW4#

    Rack10SW4#

    Rack10SW4#clear ip bgp *

    Rack10SW4#

    Rack10SW4#

    *Mar  1 02:00:04.087: %BGP-5-ADJCHANGE: neighbor 40.10.2.2 Down User reset

    *Mar  1 02:00:04.091: %BGP-5-ADJCHANGE: neighbor 40.10.4.4 Down User reset

    *Mar  1 02:00:04.091: %BGP-5-ADJCHANGE: neighbor 40.10.8.8 Down User reset

    *Mar  1 02:00:04.091: %BGP-5-ADJCHANGE: neighbor 40.10.106.6 Down User reset

    Rack10SW4#clear ip

    *Mar  1 02:00:05.175: %BGP-5-ADJCHANGE: neighbor 40.10.4.4 Up 

    *Mar  1 02:00:05.179: %BGP-5-ADJCHANGE: neighbor 40.10.106.6 Up 

    Rack10SW4#

    *Mar  1 02:00:07.227: %BGP-5-ADJCHANGE: neighbor 40.10.8.8 Up 

    *Mar  1 02:00:07.243: %BGP-5-ADJCHANGE: neighbor 40.10.2.2 Up 

    Rack10SW4#

    Rack10SW4#

    Rack10SW4#clear ip route *

    Rack10SW4#

    Rack10SW4#

    Rack10SW4#show ip bgp su

    BGP router identifier 40.10.10.10, local AS number 200

    BGP table version is 1, main routing table version 1

    33 network entries using 3861 bytes of memory

    48 path entries using 2496 bytes of memory

    15/0 BGP path/bestpath attribute entries using 2100 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 8577 total bytes of memory

    BGP activity 66/33 prefixes, 109/61 paths, scan interval 60 secs

     

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

    40.10.2.2       4   200     130     116        0    0    0 00:00:11       16

    40.10.4.4       4   200     127     116        0    0    0 00:00:14       16

    40.10.8.8       4   200     123     116        0    0    0 00:00:12       15

    40.10.106.6     4   100     122     117        0    0    0 00:00:14        0

    Rack10SW4# 

    Rack10SW4#

    Rack10SW4#show ip bgp summ

    BGP router identifier 40.10.10.10, local AS number 200

    BGP table version is 1, main routing table version 1

    33 network entries using 3861 bytes of memory

    48 path entries using 2496 bytes of memory

    15/0 BGP path/bestpath attribute entries using 2100 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 8577 total bytes of memory

    BGP activity 66/33 prefixes, 109/61 paths, scan interval 60 secs

     

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

    40.10.2.2       4   200     130     116        0    0    0 00:00:15       16

    40.10.4.4       4   200     127     116        0    0    0 00:00:17       16

    40.10.8.8       4   200     123     116        0    0    0 00:00:15       15

    40.10.106.6     4   100     122     117        0    0    0 00:00:17        0

    Rack10SW4#

    Rack10SW4#

    Rack10SW4#show ip bgp

    BGP table version is 1, local router ID is 40.10.10.10

    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

    * i28.119.16.0/24   40.10.8.8                0    100      0 100 54 i

    * i28.119.17.0/24   40.10.8.8                0    100      0 100 54 i

    * i40.10.0.0/21     40.10.2.2       4294967295    100      0 100 11 ?

    * i                 40.10.4.4       4294967295    100      0 100 11 ?

    * i40.10.2.0/24     40.10.2.2                0    100      0 i

    * i40.10.4.0/24     40.10.4.4                0    100      0 i

    * i40.10.6.0/24     40.10.8.8                0    100      0 100 i

    * i40.10.8.0/24     40.10.8.8                0    100      0 i

    * i40.10.9.0/24     40.10.2.2                2    100      0 100 ?

    * i                 40.10.4.4                2    100      0 100 ?

    *  40.10.10.0/24    0.0.0.0                  0         32768 i

    * i40.10.13.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

    * i40.10.15.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

    * i40.10.23.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

       Network          Next Hop            Metric LocPrf Weight Path

    * i40.10.25.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

    * i40.10.34.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

    * i40.10.35.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

    * i40.10.37.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

    * i40.10.39.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

    * i40.10.45.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

    * i40.10.57.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

    * i40.10.59.0/24    40.10.2.2                0    100      0 100 ?

    * i                 40.10.4.4                0    100      0 100 ?

    * i40.10.79.0/24    40.10.2.2                2    100      0 100 ?

    * i                 40.10.4.4                2    100      0 100 ?

    * i112.0.0.0        40.10.8.8                0    100      0 100 54 50 60 i

    * i113.0.0.0        40.10.8.8                0    100      0 100 54 50 60 i

    * i114.0.0.0        40.10.8.8                0    100      0 100 54 i

       Network          Next Hop            Metric LocPrf Weight Path

    * i115.0.0.0        40.10.8.8                0    100      0 100 54 i

    * i116.0.0.0        40.10.8.8                0    100      0 100 54 i

    * i117.0.0.0        40.10.8.8                0    100      0 100 54 i

    * i118.0.0.0        40.10.8.8                0    100      0 100 54 i

    * i119.0.0.0        40.10.8.8                0    100      0 100 54 i

    * i204.12.10.0      40.10.2.2               11    100      0 100 ?

    * i                 40.10.4.4               11    100      0 100 ?

    * i205.90.31.0      40.10.8.8                0    100      0 254 ?

    * i220.20.3.0       40.10.8.8                0    100      0 254 ?

    * i222.22.2.0       40.10.8.8                0    100      0 254 ?

    Rack10SW4# 

    Rack10SW4#

    Rack10SW4#show ip bgp 40.10.0.0

    BGP routing table entry for 40.10.0.0/21, version 4

    Paths: (2 available, best #2, table Default-IP-Routing-Table)

    Flag: 0x820

      Advertised to update-groups:

         1         

      100 11, (aggregated by 100 40.10.3.3)

        40.10.2.2 (metric 2) from 40.10.2.2 (40.10.2.2)

          Origin incomplete, metric 4294967295, localpref 100, valid, internal, atomic-aggregate

      100 11, (aggregated by 100 40.10.5.5)

        40.10.4.4 (metric 1) from 40.10.4.4 (40.10.4.4)

          Origin incomplete, metric 4294967295, localpref 100, valid, internal, atomic-aggregate, best

    Rack10SW4#

    Rack10SW4#

    Rack10SW4#show ip bgp

    BGP table version is 44, local router ID is 40.10.10.10

    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

    *> 28.119.16.0/24   40.10.106.6                            0 100 54 i

    * i                 40.10.8.8                0    100      0 100 54 i

    *> 28.119.17.0/24   40.10.106.6                            0 100 54 i

    * i                 40.10.8.8                0    100      0 100 54 i

    * i40.10.0.0/21     40.10.2.2       4294967295    100      0 100 11 ?

    *>i                 40.10.4.4       4294967295    100      0 100 11 ?

     

    Regards,

    Daniel

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