Ethernet MTU and TCP MSS Adjustment in the C1101-4P

[zissisktm]

Hi Community,

ISR C1101-4P connected to lan interface of ZTE H268Q (VDSL50) the problem is that some websites can't load quickly,shows connection time out and some other's load correcty.I have made adjustments with  IP TCP ADJUST-MSS 1452 and IP MTU 1492 but the problem continues to exist.What else can i config?

Thanks in advance

version 16.12
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
! Call-home is enabled by Smart-Licensing.
service call-home
platform qfp utilization monitor load 80
platform punt-keepalive disable-kernel-core
hostname R1
boot-start-marker
boot-end-marker

enable secret 9 $9$6w6wSoWA.kdTEk$aQKrkSL/X.pJTZAaXhOnDYt3y8zohNDZbyBo6/HUFoQ
no aaa new-model
ip domain name zissisnet.com

login on-success log
subscriber templating
multilink bundle-name authenticated

crypto pki trustpoint SLA-TrustPoint
enrollment pkcs12
revocation-check crl
crypto pki certificate chain SLA-TrustPoint
certificate ca 01memory free low-watermark processor 70151
diagnostic bootup level minimal
spanning-tree extend system-id
username zissis secret 9 $9$1eafdmaEFLDhGk$GPYUf5qkiu3/i6ie8HSn.sqL1ZsDP7RGOBHcGwkqEfg

redundancy
mode none

vlan internal allocation policy ascending

interface GigabitEthernet0/0/0
ip address 192.168.4.2 255.255.255.0
ip nat outside
ip tcp adjust-mss 1460
negotiation auto
interface GigabitEthernet0/1/0

interface GigabitEthernet0/1/1
!
interface GigabitEthernet0/1/2
!
interface GigabitEthernet0/1/3
!
interface Vlan1
ip address 192.168.5.1 255.255.255.0
ip nat inside
ip tcp adjust-mss 1460
!
ip default-gateway 192.168.5.1
ip forward-protocol nd
no ip http server
ip http secure-server
ip nat inside source list 1 interface GigabitEthernet0/0/0 overload
ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0/0
ip route 0.0.0.0 0.0.0.0 192.168.4.1
ip ssh version 2
!
!
!
ip access-list standard 1
10 permit 192.168.5.0 0.0.0.255

control-plane
!
banner motd ^CThis router is secure^C
!
line con 0
password 7 031E5218150632
login local
stopbits 1
line vty 0 4
login local
transport input ssh
line vty 5 15
login local
transport input ssh

[Joseph W. Doherty]

Your posted config doesn't show your revised MTU nor MSS.  So, unclear exactly what you've tried.

You do want to careful with reducing MTU to external sights as they might not get the ICMP message.

Also don't forget MSS only applies to TCP and not all traffic sets DF bit.

You might also contact your ISP and see if they can support a baby giant to support the overhead of PPPoE.

[zissisktm]

Thank you for your answer,I have tried also the operation, bridge mode the isp router and the C1104-4P made the PPPoE operation with necessary other configs and a had the same problem but when i set the mtu to 1492 on dialer interface and adjust mss to 1452 on lan interface everything was perfect.