should ip tcp adjust-mss xxx on a 2960X work?

[Tod Larson]

We recently deployed a 2960X switch in IP routing mode.  We have a couple SVIs.  We are able to configure "ip tcp adjust-mss 1300" on the SVI but it doesn't appear to to work.  Wireshark on the PC and server show the TCP ack and syn-ack both have ~1467.  I expect the adjust-mss command to re-write the TCP parameters to spoof the connecting into negotiating down to 1300, but it isn't happening.

I can't find ip tcp adjust-mss xxxx in the 2960X documentation so I'm wondering if it's a bogus command.

Should the "ip tcp adjust-mss xxxx" command work on the 2960X?

Thank you

[Georg Pauwen]

Hello,

which template are you using ? What is the output of 'show sdm prefer' ?

[Tod Larson]

I'll be able to run the command monday at work.  But we are doing it all via cli directly.  No SDM.

[Mark Malone]

I think Georg means in cli , your SDM should be set to routing as your trying to use a layer 3 command on a what can be set just as a layer 2 switch

xxxxxxxxxxx#sh sdm ?
  prefer  Show current template configuration

xxxxxxxxxxx#sh sdm prefer
 The current template is "default" template.
 The selected template optimizes the resources in
 the switch to support this level of features for
 0 routed interfaces and 255 VLANs.

  number of unicast mac addresses:                  8K
  number of IPv4 IGMP groups:                       0.25K
  number of IPv6 multicast groups:                  0.25K
  number of IPv4/MAC qos aces:                      0.375k
  number of IPv4/MAC security aces:                 0.375k
  number of IPv6 policy based routing aces:         0
  number of IPv6 qos aces:                          0
  number of IPv6 security aces:                     0.125k

Setting the SDM Template

Beginning in privileged EXEC mode, follow these steps to use the SDM template to maximize feature

usage:

After the system reboots, you can use the show sdm prefer privileged EXEC command to verify the new

template configuration. If you enter the show sdm prefer command before you enter the reload

privileged EXEC command, the show sdm prefer command shows the template in use and the template that

becomes active after a reload.

Command Purpose

Step 1 configure terminal Enter global configuration mode.

Step 2 sdm prefer {default | dual-ipv4-and-ipv6

default | lanbase-routing | qos}

Specify the SDM template to be used on the switch:

The keywords have these meanings:

• default—Gives balance to all functions.
• dual-ipv4-and-ipv6 default—Allows the switch to be used in

dual stack environments (supporting both IPv4 and IPv6).

• lanbase-routing—Supports configuring unicast routes for static

routing on SVIs.

• qos—Maximizes system resources for QoS ACEs.

Use the no sdm prefer command to set the switch to the default

template. The default template balances the use of system resources.

Note The Catalyst 2960-S switch supports only the default and

lanbase-routing templates.

Step 3 end Return to privileged EXEC mode.

Step 4 reload Reload the operating system.