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Bridge domain lab scenario

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  • 1.  Bridge domain lab scenario

    Posted 07-09-2020 14:00
    1. I have a 2 router setup: Device1---xe-4/1/16---R0--xe-/4/1/18------xe-3/0/0--R1---xe-3/0/2---------Device2
    2. Will tagged packets from device1 reach device2 which would be in same vlan for e.g. vlan 27?
    3. If so, can someone explain life of the packet? How will it traverse? Can it traverse across routers even if no ip is assigned to router interfaces? 
    4. r0: show interfaces
      xe-4/1/16 {
      vlan-tagging;
      encapsulation flexible-ethernet-services;
      unit 25 {
      encapsulation vlan-bridge;
      vlan-id 25;
      }
      unit 26 {
      encapsulation vlan-bridge;
      vlan-id 26;
      }
      unit 27 {
      encapsulation vlan-bridge;
      vlan-id 27;
      family bridge {
      filter {
      input bridge_in;
      }
      }
      }
      }
      xe-4/1/18 {
      vlan-tagging;
      encapsulation flexible-ethernet-services;
      unit 25 {
      encapsulation vlan-bridge;
      vlan-id 25;
      }
      unit 26 {
      encapsulation vlan-bridge;
      vlan-id 26;
      }
      unit 27 {
      encapsulation vlan-bridge;
      vlan-id 27;
      }
      } 
      show bridge-domains
      bd1 {
      vlan-id 25;
      interface xe-4/1/18.25;
      interface xe-4/1/16.25;
      }
      bd2 {
      vlan-id 26;
      interface xe-4/1/18.26;
      interface xe-4/1/16.26;
      }
      bd3 {
      vlan-id 27;
      interface xe-4/1/18.27;
      interface xe-4/1/16.27;
      }
      3. 
      show interfaces
      xe-3/0/0 {
          vlan-tagging;
          encapsulation flexible-ethernet-services;
          unit 25 {
              encapsulation vlan-bridge;
              vlan-id 25;
          }
          unit 26 {
              encapsulation vlan-bridge;
              vlan-id 26;
          }
          unit 27 {
              encapsulation vlan-bridge;
              vlan-id 27;
          }
      }
      xe-3/0/2 {
          vlan-tagging;
          encapsulation flexible-ethernet-services;
          unit 25 {
              encapsulation vlan-bridge;
              vlan-id 25;
          }
          unit 26 {
              encapsulation vlan-bridge;
              vlan-id 26;
          }
          unit 27 {
              encapsulation vlan-bridge;
              vlan-id 27;
          }
      }
      
      show bridge-domains
      bd1 {
          vlan-id 25;
          interface xe-3/0/0.25;
          interface xe-3/0/2.25;
      }
      bd2 {
          vlan-id 26;
          interface xe-3/0/0.26;
          interface xe-3/0/2.26;
      }
      bd3 {
          vlan-id 27;
          interface xe-3/0/0.27;
          interface xe-3/0/2.27;
      }

    #bridgedomain
    #bridging
    #mx
    #routing
    #JUNOS


  • 2.  RE: Bridge domain lab scenario
    Best Answer

    Posted 07-09-2020 15:58

     

    • Will tagged packets from device1 reach device2 which would be in same vlan for e.g. vlan 27?-- Yes, since you have created a layer 2 domain with the help of routers R0 and R1. But there won't be any inter-vlan routing happening.
    • If so, can someone explain life of the packet? How will it traverse? Can it traverse across routers even if no ip is assigned to router interfaces? -- Since you have created to a l2 network, the packet switching on l2 happens with the help of MAC address hence the routers don't refer IP header in the packet instead they refer only the ethernet header for packet delivery. The detination MAC address present in the ethernet header will be of Device2 and every transit router/device(l2 domain) will lookup in its MAC table for the outgoing interface for the concerned destination MAC address(device2).

     

     



  • 3.  RE: Bridge domain lab scenario

    Posted 08-05-2020 11:06

    Hi Nupur,

     

    Is there any limitation regarding the number of routers that can be attached to the layer 2 domain? Can more than 2 routers be included in the single layer 2 domain?

     

    Thanks,

    Vinay



  • 4.  RE: Bridge domain lab scenario

    Posted 08-05-2020 11:21

    There isn't any limitation on number of routers participating in single layer 2 domain.