Limit the rate of packed transmission on a virtual interface...

[JPFSanders]

Hi all,

I have an 877w Cisco router which is hanging from time to time and when it does
it doesn't respond to ping or process any traffic at all. The lights blink from
time to time and that is all that it does when the trouble appears.

When I check the console using the serial cable the terminal is filled with the
following error message:

%C870_FE-4-QUEUE_FULL: Ethernet Switch Module transmit queue is full

I have done some googling and the only thing I found is this doc in cisco's website

The url: is

http://www.ciscosystems.co.nz/en/US/docs/ios/12_4t/system/messages/sm_ht01.html

Inside it can be read:

---8<---

Error Message

%C870_FE-4-QUEUE_FULL : Ethernet Switch Module transmit queue is full

Explanation The switch module's transmit queue is full and packets are being dropped.

Recommended Action Reduce the rate of packet transmission to the Switched Virtual Interfaces to be less than 9 Mbps.

---8<---

That is cool because 9mps in this particular situation is fine as the router
sits on the internet border and I do not require it to do any switching other
than to route to the internet.

However how does one limit the rate of packed transmission on a virtual
interface? Or on any interface at all.

I'm banging my head against the wall with this and I would welcome any help.

Many thanks in advance.

 

[JPFSanders]

@burtsbees

Hi, I do not want to sound pedantic, but cisco says that those values are a recommendation and not mandatory. Trust me I was having lots of disconnected transfers until I did mtu = 1478 / mss = 1300.

----------------8<-----------------

From cisco:

If you are configuring the ip mtu command on the same interface as the ip tcp adjust-mss command, it is recommended that you use the following commands and values:

•ip tcp adjust-mss 1452

•ip mtu 1492

----------------8<------------------

Please, keep pointing anything you think you should, I appreciate any input that can help me as I'm really lost as to why the router ends failing every few days...

 

[JPFSanders]

Well, its been more than a week and the router has not crashed again since.

The solution I have adopted is to set the FastEthernet 0 interface to 10mb Full duplex, so far that seems to do the trick.

That way I do not have to rate limit the whole VLAN1 interface rendering the 877 switch entirely 10mb or less.

I still think this is some type of problem on the IOS, I have seen other 877 routers in similar or even heavier traffic conditions that does not exhibit this problem at all.