> Source: [sk160993](https://support.checkpoint.com/results/sk/sk160993)

# sk160993 - MSS clamping is not working properly with SecureXL

| Property | Value |
|----------|-------|
| Solution ID | sk160993 |
| Date Created | 2019-08-21 |
| Last Modified | 2019-08-27 |
| Technical Level | Advanced |
| Products | Security Gateway |
| Versions | R82.10, R82, R81.20 |
| OS | Gaia |

## Symptoms

- * MSS clamping is not working properly with SecureXL.
* The following is displayed when running tcpdump (`[Expert@firewallname]# tcpdump -i any -s0 -nn 'host 192.168.221.10 and host 192.168.44.10 and tcp[tcpflags] & (tcp-syn) != 0' -v`):

  ```
  
  192.168.44.10.64414 > 192.168.221.10.80: S, cksum 0xf8fc (correct), 3508469407:3508469407(0) win 8192 <mss 1460,nop,wscale 8,nop,nop,sackOK>
  192.168.44.10.64414 > 192.168.221.10.80: S, cksum 0xf938 (correct), 3508469407:3508469407(0) win 8192 <mss 1400,nop,wscale 8,nop,nop,sackOK>
  192.168.221.10.80 > 192.168.44.10.64414: S, cksum 0xa40a (correct), 375123064:375123064(0) ack 3508469408 win 29200 <mss 1460,nop,nop,sackOK,nop,wscale 5>
  192.168.221.10.80 > 192.168.44.10.64414: S, cksum 0xa40a (correct), 375123064:375123064(0) ack 3508469408 win 29200 <mss 1460,nop,nop,sackOK,nop,wscale 5>
  ```

## Cause

MSS_clamping works on one of the interfaces but not on the other.

## Solution

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