what does Coll (collission) represent in `netstat -ni`

[skt_skt]

B.11.23
ia64 hp server rx6600


Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll
lan0 1500 147.154.10.0 147.154.10.82 3956301 0 3258935 0 18960

lanadmin -x 0
Speed = 100 Full-Duplex.
Autonegotiation = Off.

Does that mean more traffic than 100Mbps LAn can accomdate? Or what else?

[Patrick Wallek · Accepted solution]

Definitions of a collision:

http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci211814,00.html#

http://bugclub.org/beginners/networking/collision.html

[Steven E. Protter]

Shalom,

It's like a head on car crash.

Both packets are destroyed and need to be re-transmitted.

In networking a collision domain is defined by how many network cards are within the lan or vlan.

If the collision domain is too large, too many collisions. Network folks segment LAN's into smaller collision domains to avoid this.

As a systems administrator, all you can do is ask networking to resolve the issue.

SEP

[rick jones]

There should never be any collisions recorded by a device in full-duplex mode. That netstat -ni is showing Coll(isions) on a full-duplex link suggests that either netstat or its data source is buggy. You should make sure you have the latest transport and driver patches installed, and if it still persists in reporting Coll(isions) for a full-duplex interface you will want to fire-up your support contract and log a call with the Response Center.

BTW, the NICs supported in an rx6600 should be _MORE_ than capable of auto speed sensing and autonegotiating duplex settings - there should be no need at all to hardcode. That being the case, another thing you may want to check into is putting both the NIC and its switch port back to autoneg.

[skt_skt]

autoneg or hardcode settings are used only at the beginning when the host and switch start communication; Once the speed is determied it is no longer. So autoneg does not cause coll after that.isn't it??

[rick jones]

Knuth only knows what stats end-up where in the event of a duplex mis-match between the NIC and the switch.

[Bill Hassell]

> autoneg or hardcode settings are used only at the beginning when the host and switch start communication; Once the speed is determied it is no longer. So autoneg does not cause coll after that.isn't it??

Collisions are only possible in half-duplex communication. Autonegotiation only works reliably when both sides are configured to autonegotiation. Since your rx6600 is not negotiating, the switch is probably set to autonegotiate and will fail. The speed will be correct but the protocol standard dictates that autonegotiation fall back to half duplex. That will cause massive collisions and a lot of other communication errors (see the stats in lanadmin).

You must set both ends to autonegotiate or you must set both ends to 100 FD. In your current setting, you will be lucky to see more than 5-8 Mbit throughput.

[skt_skt]

I havd 100FD hard coded on both side.

[skt_skt]

I did not understand "Knuth only knows what stats end-up where in the event of a duplex mis-match between the NIC and the switch."

[Patrick Wallek]

If you do another 'netstat -in' command, is the Coll number increasing?

You should not be getting collisions of both ends really are at 100FD.

[skt_skt]

Its not increasing now; Not sure when did last collission happened. But as per the logs it did not imcrease since a week.

[Dennis Handly]

>I did not understand "Knuth only knows what

Knuth is a famous software god. And if he doesn't know, nobody does. ;-)