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Unable to ping WAN interface after bridging VLAN on EXOS switch

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TitleUnable to ping WAN interface after bridging VLAN on EXOS switch
Symptoms
  • No iparp entry for WAN interface device
  • Ping timeouts to WAN interface device
  • WAN interface device MAC learned in expected VLAN
  • L2 functional
Environment
  • Summit: All
  • EXOS: All
  • Untangle Box
  • VLAN Bridging
Cause
When an untangle box is used in-line to bridge VLANs it is necessary to make two connections from switch to untangle box as seen below.  Traffic is expected to travel as follows:
  1. Ingress P3 untagged (UT) on Switch
  2. Egress P1 untagged (UT) into Untangle box
  3. Ingress P2 untagged (UT) on switch from Untangle box
  4. Egress P52 Tagged to WAN
However the switch will not learn an ARP entry for the Wan uplink as the switch only has an IP on the Vlan 2 interface and not the Vlan 3 interface.

Topology Diagram

VLAN 1: IP 1.1.1.1/24
VLAN 2: IP 2.2.2.1/24
VLAN 3: No IP
WAN IP: 2.2.2.2/24 (same subnet as VLAN 2)
Resolution
To resolve this and see traffic flow as expected a static arp entry for the Wan device will need to be added.
  1. configure iparp add <ip-address> <mac-address
The traffic will now take the expected path (e.g. In P3, out P1, in P2, and finally out P52)
 
Additional notes
Issuing the command "show fdb port 52" should see the MAC of the Wan device prior learned in vlan 3 but not vlan 2 prior to adding static arp.  Once the static arp is added the Wan device will then be learned on P1

*NOTE: Please understand that this is a basic example.

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