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Cisco Bug: CSCup12983 - RSP1 : Issues with MTU setting on POS with MPLS

Last Modified

Jan 29, 2017

Products (1)

  • Cisco ASR 900 Series Aggregation Services Routers

Known Affected Releases

15.3(3)S

Description (partial)

Symptom:
Issues with MTU settings on POS interface

Conditions:
1.	On fresh config [ reload and config ], everything works fine. It has been tested with L3VPN configs with MPLS over POS in core.
2.	Set the MPLS MTU now and send jumbo frames from IXIA. This also works. Fragmentation takes place and packets are received fine.
3.	Now, unconfigure the POS interface and recreate it with all the same configs.
4.	Packets more than 1511 do not go out (input Ethernet packet size 1518)
5.	The interface MTU is set at 1511 regardless of the configuration
6.	Unsetting and resetting the MPLS MTU on the POS interface, sets MTU to corresponding value. However, in this case fragmentation does not work
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