[j-nsp] GigE: M10 <-> Cisco Catalyst 6509: oversized and corrupted frames

[Matti Saarinen]

I've connected Juniper M10 (JUNOS 5.6R2.4) and Cisco Catalyst 6509
(IOS 12.1(13)E4) to each other via gigabit ethernet using multimode
fibre. Both ends complain about the packets they are seeing. On M10,
the number in oversized frames counter increases. The 6509 complains
about corrupted IP packets, too.

I did check the MTUs but they are the same on the both ends. There are
no other errors which could be the cause of this beaviour.

The relevant counters on M10 look like this:

> show interfaces ge-0/1/0 extensive    
Physical interface: ge-0/1/0, Enabled, Physical link is Up
  Interface index: 14, SNMP ifIndex: 17, Generation: 13
  Link-level type: Ethernet, MTU: 1518, Speed: 1000mbps, Loopback: Disabled,
[cut]
  MAC statistics:                      Receive         Transmit
    Total octets                   49678735078      23364511178
    Total packets                    264424668        266312599
    Unicast packets                  259715065        265837157
    Broadcast packets                      242            17960
    Multicast packets                  4362526           457482
    CRC/Align errors                         0                0
    FIFO errors                              0                0
    MAC control frames                       0                0
    MAC pause frames                         0                0
    Oversized frames                    346835
    Jabber frames                            0
    Fragment frames                          0
    VLAN tagged frames               263506071
    Code violations                          0



Cisco just logs this:

%MLS_STAT-SP-4-IP_CSUM_ERR: IP checksum errors


The local Cisco support informed me that sometimes Juniper sends GigE
packets too rapidly. I understood this so that sometimes the interval
between two frames Juniper sends is shorter than the GigE specs allow.
Is anyone able to confirm that information? I've no reason not to
believe that, but I'm curious whether anyone else has encountered the
same problem. Also, I'm very interested in finding a workaround.

Cheers,

-- 
- Matti -