I will apologize in advance if there is a better community for this question, I guessed as to where it could go.
Background
- We have a number of locations which we have extended our Fabric.
- 21 locations that connect to our CORE via a subscribed L3 service.
- The service handles routes to each node by static route definition.
- The service has a subscribed MTU of 3900.
- 4 locations that connect to our CORE via dark fiber or a shared L2 service (METRO) where the VLAN ids are unique to the fiber use partners.
- We've extended the fabric from our CORE (VSP7400s) to each of the locations which can be a VSP4900 or XA14800 depending on that location.
- All system MTUs are 1950.
- ISIS Adjacencies are up.
- ISIS LSDB shows all locations.
- ISIS SPBM I-SID shows all currently active C-VLANs with I-SIDs.
- L2 VSN traffic works with the conditions described below.
Issue Description
- L2 VSNs between dark fiber/L2 service connected locations have no issue with any flows.
- L2 VSNs between the L3 subscribed service connected locations have no issue as long as the MTU doesn't exceed a given value.
- Example:
- (Windows 10 System)
- [WORKS] ping A.B.C.D -l 1470
- [FAILS] ping A.B.C.D -l 1741
Troubleshooting
- Verified MTU settings between L3 subscribed service connected locations:
- (Windows 10 System)
- [WORKS] ping A.B.C.D -l 1472 -f
- A.B.C.D is a non-fabric endpoint reached via L3 subscribed service.
- Removed 2 devices reachable via the L3 subscribed service from our main fabric and created a new one between those devices themselves.
- Used multiple incrementing values per test for command on both sides of fabric:
- logical-intf isis 1 dest-ip A.B.C.D mtu ABCD
- ABCD --> 1950, 2000, 2050
- Same results.
- Changed the fabric endpoints to both be XA1480s and recreated a fabric between them.
QuestionCan someone recommend some testing or have ideas on how to solve this issue?
Thank you in advance.
