Example: Configuring The Tcp Mss Adjustment - Cisco ASR 1000 Series Configuration Manual

Configuring TCP

Example: Configuring the TCP MSS Adjustment

Example: Configuring the TCP MSS Adjustment
The following example shows how to configure and verify the interface adjustment value for the example
topology displayed in the figure below:
Figure 2: Example Topology for TCP MSS Adjustment
Configure the interface adjustment value on router B:
Router_B(config)# interface GigabitEthernet 2/0/0
Router_B(config-if)# ip tcp adjust-mss 500
Telnet from router A to router C with B having the Maximum Segment Size (MSS) adjustment configured:
Router_A# telnet 192.168.1.1
Trying 192.168.1.1... Open
Observe the debug output from router C:
Router_C# debug ip tcp transactions
Sep 5 18:42:46.247: TCP0: state was LISTEN -> SYNRCVD [23 -> 10.0.1.1(38437)]
Sep 5 18:42:46.247: TCP: tcb 32290C0 connection to 10.0.1.1:38437, peer MSS 500, MSS is 500
Sep 5 18:42:46.247: TCP: sending SYN, seq 580539401, ack 6015751
Sep 5 18:42:46.247: TCP0: Connection to 10.0.1.1:38437, advertising MSS 500
Sep 5 18:42:46.251: TCP0: state was SYNRCVD -> ESTAB [23 -> 10.0.1.1(38437)]
The MSS gets adjusted to 500 on Router B as configured.
The following example shows the configuration of a Point-to-Point Protocol over Ethernet (PPPoE) client
with the MSS value set to 1452:
Device(config)# vpdn enable
Device(config)# no vpdn logging
Device(config)# vpdn-group 1
Device(config-vpdn)# request-dialin
Device(config-vpdn-req-in)# protocol pppoe
Device(config-vpdn-req-in)# exit
Device(config-vpdn)# exit
Device(config)# interface GigabitEthernet 0/0/0
Device(config-if)# ip address 192.168.100.1.255.255.255.0
Device(config-if)# ip tcp adjust-mss 1452
Device(config-if)# ip nat inside
Device(config-if)# exit
Device(config)# interface ATM 0
Device(config-if)# no ip address
Device(config-if)# no atm ilmi-keepalive
Device(config-if)# pvc 8/35
IP Application Services Configuration Guide, Cisco IOS XE Release 3S (Cisco ASR 1000)
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