Attempting to connect to a large telecom vendor's MPLS network using MLPPP over 2 T1s and OSPF routing protocol with our Adtran 3450 running AOS R10.6.0. Previous non-Cisco, non-Adtran router works perfectly; replacement with Adtran 3450 experiences loss of adjacency over MLPPP link to vendor's Cisco IOS XR-based router at random timings from 2 to 8 minutes. MPLS vendor says dead timer is timing out. Adtran "debug ip ospf" shows link drops from FULL to INIT to EXSTART to FULL adjacency. Dropping down to one T1 active and OSPF will stay stable. Vendor requires PPP fragmentation to be disabled, which appears to be the default for AOS. MTU on the MLPPP is set for default of 1500.
After working up from Tier 1 support at large vendor, got to Tier 3. I let them know that I had another Adtran 3450 running MLPPP with two T1s and OSPF with no adjacency issues, and has been running that way for a year. In reviewing, the engineer found the working Adtran was interfaced with a Juniper M320 router platform.
The vendor then moved the MLPPP connection from the Cisco IOS XR platform to the Juniper platform, which resolved the issue.
It appears that there are serious Cisco IOS XR interoperability issues with MLPPP and Adtran Netvanta routers. Not sure, but in another similar case the vendor said they are running Cisco IOS XR v 3.8.2.
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