[j-nsp] MTU mismatch between EX4200 and EX4500 / OSPF3 adjacencies

[Laurent CARON]

Hi,

I'm setting up ospf3 between EX4200 and EX4500.

On 4500 I have:
set interfaces ae26 vlan-tagging
set interfaces ae26 aggregated-ether-options lacp active
set interfaces ae26 aggregated-ether-options lacp periodic fast
set interfaces ae26 unit 6 vlan-id 6
set interfaces ae26 unit 6 family inet address 10.10.0.153/30
set interfaces ae26 unit 6 family inet6 address aaaa:bbbb:ffa1:0e6f::2d/126
set interfaces ae26 unit 901 vlan-id 901
set interfaces ae26 unit 901 family inet address 172.31.253.121/30
set interfaces ae26 unit 901 family inet6 address 
aaaa:bbbb:0000:feff:feff:feff:fef5:0231/126
set protocols ospf area 172.31.253.0 interface ae26.901
set protocols ospf3 area 172.31.253.6 interface ae26.901


On 4200 I have:
set interfaces ae26 vlan-tagging
set interfaces ae26 aggregated-ether-options lacp active
set interfaces ae26 aggregated-ether-options lacp periodic fast
set interfaces ae26 unit 6 vlan-id 6
set interfaces ae26 unit 6 family inet address 10.10.0.154/30
set interfaces ae26 unit 6 family inet6 address aaaa:bbbb:ffa1:0e6f::2e/126
set interfaces ae26 unit 901 vlan-id 901
set interfaces ae26 unit 901 family inet address 172.31.253.122/30
set interfaces ae26 unit 901 family inet6 address 
aaaa:bbbb:0000:feff:feff:feff:fef5:0232/126
set protocols ospf area 172.31.253.0 interface ae26.901
set protocols ospf3 area 172.31.253.6 interface ae26.901

On 4200:
 > show interfaces ae26 extensive detail | match mtu
   Link-level type: Ethernet, MTU: 1518, Speed: 20Gbps, BPDU Error: 
None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: 
Disabled, Flow control: Disabled, Minimum links needed: 1, Minimum 
bandwidth needed: 0
     Carrier transitions: 2, Errors: 0, Drops: 0, MTU errors: 0, 
Resource errors: 0
     Protocol inet, MTU: 1500, Generation: 212, Route table: 6
     Protocol inet6, MTU: 1500, Generation: 213, Route table: 6
     Protocol inet, MTU: 1500, Generation: 211, Route table: 0
     Protocol inet6, MTU: 1504, Generation: 222, Route table: 0

On 4500:
 > show interfaces ae26 extensive detail | match mtu
   Link-level type: Ethernet, MTU: 1518, Speed: 20Gbps, BPDU Error: 
None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: 
Disabled, Flow control: Disabled, Minimum links needed: 1, Minimum 
bandwidth needed: 0
     Carrier transitions: 14, Errors: 0, Drops: 0, MTU errors: 0, 
Resource errors: 0
     Protocol inet, MTU: 1500, Generation: 1852, Route table: 7
     Protocol inet6, MTU: 1500, Generation: 1853, Route table: 7
     Protocol inet, MTU: 1500, Generation: 1843, Route table: 0
     Protocol inet6, MTU: 1500, Generation: 1915, Route table: 0


We clearly see a MTU mismatch (1500 vs 150*4* for inet6 on the 4200 
side) leading to OSPF adjacencies not coming up.

Setting:
set interfaces ae26 mtu 1518
on the 4200 side allows to have the OSPF adjacencies up.

Did you guys experience such bahavior ?

4200 are running 12.3R8.7
4500 is running 12.3R7.7

Thanks

Laurent