Dell Networking: OS10 PBR Misrouting in VLT Environments using VLTi Interfaces

Summary: A user encountered an issue with Policy-Based Routing (PBR) in a Virtual Link Trunking (VLT) environment using Dell OS10 switches. When traffic is routed to the VLT-secondary switch using VLTi interfaces, it results in "communication" errors. The issue was resolved by disabling PBR on the VLT domain. There is a workaround by restructuring the route-map configuration using two Access Control Lists (ACL) to separate traffic paths. ...

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Symptoms

Information Collection

Use these commands for live troubleshooting:

  
show mac address-table
show ip arp
show ip route
show running-config route-map
show running-config access-list
show running-config vlt

Consider creating ACLs to match the traffic (source/destination) and verify if the traffic is taking the expected path.

Collect the support bundle for further analysis.

 

Issue Identification

  • Communication fails when there is asymmetric traffic using VLTi interfaces.
  • Time To Live (TTL) exceeded messages may be observed.
  • Traffic works correctly when it uses only one VLT peer switch.

Cause

Root Cause

In an asymmetric communication, when traffic is routed through the VLTi on switch 1, switch 2 may send the traffic to the wrong destination, causing communication issues. This happens because PBR matches the traffic on switch 2's VLTi interfaces.

Resolution

Dell SmartFabric OS10 User Guide Release 10.6.0

 

  • Disable PBR on the VLT domain:
  
ip pbr disable
ipv6 pbr disable

PBR configuration

 

Workarounds

  • Reconfigure a route-map using two ACLs:
    • ACL1: Permit entries for subnets using traditional routing.
    • ACL2: ip permit any any for traffic to be filtered.
    • Route-map:
route-map ToDefaultRoute deny 10
  match ip address ACL1
route-map ToFwPbr permit 20
  match ip address ACL2
  set ip next-hop next-hop IP

Videos

Affected Products

SmartFabric OS10 Software
Article Properties
Article Number: 000357162
Article Type: Solution
Last Modified: 20 Aug 2025
Version:  1
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