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6-14
Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
Chapter 6 Configuring PPPoE over Ethernet and IEEE 802.1Q VLAN
TCP MSS Adjust
TCP MSS Adjustment Configuration: Examples
Figure 1 Example Topology for TCP MSS Adjustment
The following example shows how to configure and verify the adjustment value. Configure the interface
adjustment value on router B:
Router_B(config)# ip pxf adjust-mss 500
Telnet from router A to router C, with B having the 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 PPPoE client with the MSS value set to 1452:
vpdn enable
no vpdn logging
!
vpdn-group 1
request-dialin
protocol pppoe
ip pxf adjust-mss 1452
!
interface Ethernet0
ip address 192.168.100.1.255.255.255.0
ip nat inside
!
interface ATM0
no ip address
no atm ilmi-keepalive
pvc 8/35
pppoe client dial-pool-number 1
!
dsl equipment-type CPE
dsl operating-mode GSHDSL symmetric annex B
dsl linerate AUTO
Router A
Ethernet0/0
IP Address
10.0.1.1 255.255.255.0
Interface Ethernet 0/0
IP Address
192.168.1.1 255.255.255.0
Ethernet2/0
IP Address 10.0.1.2 255.255.255.0
TCP MSS 500
Router C
Router B
170888