[c-nsp] Cisco 7500, output errors on FastEth interfaces

[Ted Mittelstaedt]

This is a common problem with Cisco.  Many of their port cards are
NOT autosensing.  They hard-code to a specific speed and duplex.  The
autosensing ones allow you to set "auto" on the adapter, the others
won't.

If you plug an ethernet port that is hard coded into a typical switch
that
has autosensing ports, you will get errors.  This is due to the switch
continuing to try the Nway auto probing and the router's port ignoring
it.

The only solution is to use managed switches and go into their
management interface and hard-code the port to the same speed and
duplex setting as what the router is at.

You will also get the same problem if the Cisco port is autosensing and
you have set it to auto, and you plug into a switch that is hard-coded to
a specific speed and duplex.

And you get the same problem if you plug a PC ethernet card into an
autosensing switch port and go into the WIndows ethernet card properties
and hard-code the speed.

And, one last thing, please no comments from the peanut gallery.  Yes
I know that Nway is supposed to handle this.  In real life it doesen't
usually.

Ted

>-----Original Message-----
>From: cisco-nsp-bounces at puck.nether.net
>[mailto:cisco-nsp-bounces at puck.nether.net]On Behalf Of Ray Van Dolson
>Sent: Tuesday, August 30, 2005 10:33 PM
>To: cisco-nsp at puck.nether.net
>Subject: [c-nsp] Cisco 7500, output errors on FastEth interfaces
>
>
>Hello all... I am definitely not a Cisco admin, but it has been
>kind of forced
>upon me and I'm trying to get up to speed as quickly as
>possible.  Hoping to
>find some help here as well as reading up elsewhere.
>
>We've got a Cisco 7500 series router with an RSP4, and two
>VIP4-50's.  A HSSI
>port connected to a T3 is on one of the VIP4-50's and the other
>contains two
>FastEthernet ports.
>
>The router had been suffering from ddos attacks for a while and wasn't
>handling things too well.  In fact it's CPU load was up around
>75% through
>even "normal" traffic times.
>
>Investigating this it seemed we weren't using the proper
>switching method.
>Turned on "ip cef distributed" which apparently offloads a lot of the
>switching decisions to the VIP cards.  Immediately the load on the RSP4
>dropped to 2%.  Hoorah right?
>
>Things seem to be working OK, but now I am beginning to see
>output errors on
>the FastEthernet interfaces.  I'm wondering if this is due to
>the cef entry I
>enabled above.
>
>Should I turn on ip route-cache distributed for the Hssi port
>only and use
>another method for the FastEthernet ports?  If I understand
>things correctly,
>turning ip cef distributed on globally will enable this on all
>interfaces.
>
>In any case, the config for the FastEth ports is pretty basic:
>
>interface FastEthernet5/1/0
> ip address XX.XXX.XXX.1 255.255.255.0
> ip access-group 182 in
> no ip proxy-arp
> no ip mroute-cache
> half-duplex
> hold-queue 100 in
>
>Similar for the other one.
>
>Any suggestions?
>
>Ray
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