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routes via sham-link are hidden

  • 1.  routes via sham-link are hidden

    Posted 06-19-2021 11:57
    I have the following topology
    I created a sham-link between R2 and R4. I verified it as follows:
    root@R4# run show ospf interface instance CE1 detail
    Interface           State   Area            DR ID           BDR ID          Nbrs
    ge-0/0/2.0          DR      0.0.0.0         192.168.168.4   172.16.6.6         1
      Type: LAN, Address: 10.50.0.6, Mask: 255.255.255.252, MTU: 1500, Cost: 1
      DR addr: 10.50.0.6, BDR addr: 10.50.0.5, Priority: 128
      Adj count: 1
      Hello: 10, Dead: 40, ReXmit: 5, Not Stub
      Auth type: None
      Protection type: None
      Topology default (ID 0) -> Cost: 1
    shamlink.0          PtToPt  0.0.0.0         0.0.0.0         0.0.0.0            1
      Type: P2P, Address: 0.0.0.0, Mask: 0.0.0.0, MTU: 0, Cost: 1
      Local: 192.168.168.4, Remote: 192.168.168.2
      Adj count: 1
      Hello: 10, Dead: 40, ReXmit: 5, Not Stub
      Auth type: None
      Protection type: None, No eligible backup
      Topology default (ID 0) -> Cost: 1
    
    
    root@R4# run show ospf neighbor instance CE1 detail
    Address          Interface              State     ID               Pri  Dead
    10.50.0.5        ge-0/0/2.0             Full      172.16.6.6       128    38
      Area 0.0.0.0, opt 0x52, DR 10.50.0.6, BDR 10.50.0.5
      Up 00:05:12, adjacent 00:05:12
    192.168.168.2    shamlink.0             Full      192.168.168.2      0    32
      Area 0.0.0.0, opt 0x52, DR 0.0.0.0, BDR 0.0.0.0
      Up 00:05:12, adjacent 00:05:07
    
    root@R4# run show ospf database instance CE1
    
        OSPF database, Area 0.0.0.0
     Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
    Router   10.50.0.1        10.50.0.1        0x80000004  1150  0x22 0xc871  36
    Router   10.50.0.6        10.50.0.6        0x80000004   715  0x22 0xf035  36
    Router   172.16.5.1       172.16.5.1       0x80000008   400  0x22 0x4b4c  72
    Router   172.16.6.6       172.16.6.6       0x80000006   331  0x22 0xb0cc  72
    Router   192.168.168.2    192.168.168.2    0x80000005   326  0x22 0x8a5a  48
    Router  *192.168.168.4    192.168.168.4    0x80000004   325  0x22 0xb821  48
    Network  10.50.0.1        192.168.168.2    0x80000001   401  0x22 0xf91b  32
    Network *10.50.0.6        192.168.168.4    0x80000001   330  0x22 0x23e2  32
    Network  192.168.1.5      172.16.5.1       0x80000001   706  0x22 0x3448  32
    ​

    But the routes via sham-link are hidden
    root@R4# run show route table CE1.inet.0 hidden
    
    CE1.inet.0: 11 destinations, 15 routes (11 active, 0 holddown, 3 hidden)
    + = Active Route, - = Last Active, * = Both
    
    10.50.0.0/30        [OSPF] 00:06:01, metric 2
                        > via shamlink.0
    172.16.5.0/24       [OSPF] 00:06:01, metric 2
                          to 10.50.0.5 via ge-0/0/2.0
                        > via shamlink.0
    172.16.5.1/32       [OSPF] 00:06:01, metric 2
                          to 10.50.0.5 via ge-0/0/2.0
                        > via shamlink.0
    
    
    root@R4# run show route table CE1.inet.0 hidden detail
    
    CE1.inet.0: 11 destinations, 15 routes (11 active, 0 holddown, 3 hidden)
    10.50.0.0/30 (2 entries, 1 announced)
             OSPF
                    Next hop type: Router
                    Address: 0x965c9e8
                    Next-hop reference count: 1
                    Next hop: via shamlink.0, selected
                    Session Id: 0x0
                    State: <Hidden Int AlwaysFlash>
                    Inactive reason: Unusable path
                    Age: 6:11       Metric: 2
                    Validation State: unverified
                    Area: 0.0.0.0
                    Task: CE1-OSPF
                    AS path: I
                    Communities: rte-type:0.0.0.0:1:0
    
    172.16.5.0/24 (2 entries, 1 announced)
             OSPF
                    Next hop type: Router
                    Address: 0x95a42f8
                    Next-hop reference count: 2
                    Next hop: 10.50.0.5 via ge-0/0/2.0
                    Session Id: 0x0
                    Next hop: via shamlink.0, selected
                    Session Id: 0x0
                    State: <Hidden Int AlwaysFlash>
                    Inactive reason: Unusable path
                    Age: 6:11       Metric: 2
                    Validation State: unverified
                    Area: 0.0.0.0
                    Task: CE1-OSPF
                    AS path: I
                    Communities: rte-type:0.0.0.0:1:0
    
    172.16.5.1/32 (2 entries, 1 announced)
             OSPF
                    Next hop type: Router
                    Address: 0x95a42f8
                    Next-hop reference count: 2
                    Next hop: 10.50.0.5 via ge-0/0/2.0
                    Session Id: 0x0
                    Next hop: via shamlink.0, selected
                    Session Id: 0x0
                    State: <Hidden Int AlwaysFlash>
                    Inactive reason: Unusable path
                    Age: 6:11       Metric: 2
                    Validation State: unverified
                    Area: 0.0.0.0
                    Task: CE1-OSPF
                    AS path: I
                    Communities: rte-type:0.0.0.0:1:0
    
    [edit]
    root@R4#
    ​


    Appreciate any insights !!



  • 2.  RE: routes via sham-link are hidden

    Posted 06-19-2021 12:26
    I found a previous post shamlink hidden in vpn.inet.0, I am trying to understand it.
    I used to do a lab in Cisco topology as follows:

    the following shows the difference with or without sham-link
    Wihtout sham link, go via serial link
    
    R5(config)#do show ip route 6.6.6.6
    Routing entry for 6.6.6.6/32
      Known via "ospf 10", distance 110, metric 65, type intra area
      Last update from 10.10.10.6 on Serial2/0, 00:00:30 ago
      Routing Descriptor Blocks:
      * 10.10.10.6, from 6.6.6.6, 00:00:30 ago, via Serial2/0
          Route metric is 65, traffic share count is 1
    
    R5(config)#do show ip route | i 6.6.6.6
    O        6.6.6.6 [110/65] via 10.10.10.6, 00:01:52, Serial2/0
    
    With sham link, go via MPLS 
    R5(config)#do show ip route 6.6.6.6
    Routing entry for 6.6.6.6/32
      Known via "ospf 10", distance 110, metric 22, type intra area
      Last update from 172.16.2.2 on Ethernet0/2, 00:00:58 ago
      Routing Descriptor Blocks:
      * 172.16.2.2, from 6.6.6.6, 00:00:58 ago, via Ethernet0/2
          Route metric is 22, traffic share count is 1
    
    R5(config)#do show ip route | i 6.6.6.6
    O        6.6.6.6 [110/22] via 172.16.2.2, 00:02:22, Ethernet0/2
    ​

    I am trying to understand whether I could do the same in the Juniper.

    thanks !!





  • 3.  RE: routes via sham-link are hidden

    Posted 06-19-2021 12:35
    got it. 

    root@R6# run traceroute 172.16.5.1
    traceroute to 172.16.5.1 (172.16.5.1), 30 hops max, 40 byte packets
     1  10.50.0.6 (10.50.0.6)  19.902 ms  4.833 ms  1.999 ms
     2  * * *
     3  10.51.0.1 (10.51.0.1)  24.668 ms  5.841 ms  4.480 ms
         MPLS Label=299824 CoS=0 TTL=1 S=1
     4  172.16.5.1 (172.16.5.1)  18.461 ms  4.809 ms  4.683 ms
    ​

    thanks a lot !!