PPP unusual errors

[timt]

Hi all,
I've started getting unusual errors in my ppp log as shown below. Sometimes these cause ppp to disconnect. PPP then has to be reconnected manually. Any ideas ?

thanks
Tim
Nov 5 16:35:27 ppp [wan] error writing len 1502 frame to b0: Message too long
Nov 5 16:35:27 ppp [wan_link0] rec'd unexpected protocol Padding Protocol, rejecting
Nov 5 16:35:24 ppp [wan] error writing len 1502 frame to b0: Message too long
Nov 5 16:35:24 ppp [wan_link0] rec'd unexpected protocol RTP IPHC Full Header, rejecting
Nov 5 16:35:10 ppp [wan] error writing len 1502 frame to b0: Message too long
Nov 5 16:35:10 ppp [wan_link0] rec'd unexpected protocol Cisco Systems, rejecting
Nov 5 16:35:08 ppp [wan_link0] rec'd unexpected protocol Appletalk, rejecting
Nov 5 16:01:53 ppp [wan] error writing len 1502 frame to b0: Message too long
Nov 5 16:01:53 ppp [wan_link0] rec'd unexpected protocol RTP IPHC Full Header, rejecting
Nov 5 14:23:13 ppp [wan] error writing len 1502 frame to b0: Message too long
Nov 5 14:23:13 ppp [wan_link0] rec'd unexpected protocol 0x1021, rejecting

[stephenw10]

Link MTU not set correctly? It seems to be complaining about packets that are too large.

What sort of connection is that?

Steve

[timt]

Hi Steve,
The connection is a PPPOE connection out over my ISP's ethernet. I thought it might be an MTU issue and double checked the MTU set on the link and it is set to 1492.

The underlying interface is still 1500 and I was tempted to set that to 1492 as well to see if those messages go away, but I've never seen the underlying link affect a PPPOE over the top of it before.

I was more concerned with other protocols turning up on the link! I haven't seen that before and I've had this link for years.

I might ask support at my ISP if something weird is happening at their end.

regards
Tim

[stephenw10]

Hmm, try a pcap on the parent interface, try to capture a few.

It would not surprise me if it's reading those wrong because they truncated.

Steve

[timt]

@stephenw10
Good idea, I'll take a look in Wireshark at the result, that might give some clues.

I removed the hardset 1492 MTU from the config and let PPP negotiate the MTU. It still came up 1492 as expected.

Its odd that it only happens in bursts, the first about an hour after resetting the link. I haven't seen anything since.

I've also asked the ISP if there is anything happening at their end just in case.

regards
Tim