1600 Collisions

[c1utch]

I'm working with my ISP on a connection issue between my LAN and their location. I'm using a Sonicwall SOHO3 as my firewall, which is attached to a CISCO 1600 series router. Our T1 is plugged directy into our CISCO 1600 router.

While we were troubleshooting this problem, a tech from my ISP connected to our CISCO 1600 router and noticed a lot of collisions occuring on the router. He also noted CRC errors on our serial interface. The serial interface is plugged into our SOHO3 firewall. He mentioned that the CISCO 1600 routers are only 10MB/half duplex. He said that the traffic between the router and the firewall (which is 100MB/full duplex) is colliding because of the half duplex interface on the router not being able to communicate with the firewall efectively.

I can change the settings on the SOHO3's interface to match the CISCO router...changing it from Autonegotiate to 10MB/half duplex. However, rather than going "backwards" with the firewall, isn't there a way for me to change the serial interface on the CISCO router to at least Full Duplex? The tech from my ISP said that the CISCO 1600 series routers don't support Full Duplex for that interface. He told me to go out and buy a 1700 series router.

Thanks.

Chris

 

[routerman]

Chris,

Your Techie is talking about the LAN interface, not the serial port. The LAN port on the 1600 can only run 10meg Half duplex. If you want 100 Full you need a later router, 1700 series etc.

As for the CRC errors on the serial, issue the `clear counter ' command and monitor for a day or so. If the errors are incrementing you may have a defective ISP link or possibly a defective router port.

 

[c1utch]

Ok. I think the tech cleared the counters last night and then watched as more CRC errors starting poping up. The phone company took down the T1 last night and then rebuilt it to check if any errors come up. Its back up this morning but haven't talked to the ISP tech yet. However, I'm still seeing long response times pop up at the router interface to the T1 when I do some standard trace routes to an internet IP address. (occasional 200-240ms response times...just occasional though)

Does it matter that the firewall interface is set to Autonegotiate and the router can only use 10MB/half duplex? You would think Autonegotiate means what it says...but should I drop it to 10MB/half duplex? I guess it won't hurt to try and then see if those long response times go away.

Thought about waiting to try that though until I hear back from the ISP tech though on the results from the phone company.

Chris

 

[eurobadger]

Hi

As you say, it is well worth fixing the speed & duplex when connecting together devices from different manufacturers. The negotiation is not standardised, and a mismatch typically results in slow communications with lots of collisions

EB