Hello
I have been trying to increase the PPPOE MTU for my OpenWRT 21.02.1
I am able to manually set the MTU in openwrt side (using ip link set dev eth1.835 mtu 1540) but not for the
dynamically created pppoe-wan interface (still at 1492)
What prevents me to successfully establish a session with MTU > 1500 is that the PADI
packets (regardless of my setting) send by OpenWrt. They include the tag PPP-Max-Payload = 1500
The network provider in my case needs this value to be > 1500 otherwise reverts back to 1500 for PPPoE and 1492 for PPP MTU.
Has anyone been successful in modifying the value of PPP-Max-Payload sent during PADI request ?
I have been experimenting with different config MTU values but always using tcpdump I see that the PPP-Max-Payload value sent in PADI is 1500
My config is very basic
config interface 'wan'
option ifname 'eth1.835'
option proto 'pppoe'
option username 'xxxxx@y.y.y.y.com'
option password 'pass'
option keepalive '10 30'
option mtu 1540
The result is:
eth1.835 Link encap:Ethernet HWaddr 0C:6A:F7:63:00:01
inet6 addr: fe80::e6a:f7ff:fe63:1/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1540 Metric:1
RX packets:16 errors:0 dropped:0 overruns:0 frame:0
TX packets:27 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1059 (1.0 KiB) TX bytes:2155 (2.1 KiB)
pppoe-wan Link encap:Point-to-Point Protocol
inet addr:10.0.123.51 P-t-P:85.100.125.103 Mask:255.255.255.255
inet6 addr: fe80::d4c9:a310:76f8:9e1e/128 Scope:Link
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1492 Metric:1
RX packets:8 errors:0 dropped:0 overruns:0 frame:0
TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:3
RX bytes:563 (563.0 B) TX bytes:718 (718.0 B)
Thak you all
The ISP must also support this. Anyway this works for me on Globe Fiber (GPON, with their modem in bridge mode) in the Philippines with OpenWRT 22.03.0-rc6 on a Linksys E8450.
EDIT: sorry, I misread the request. You are asking for MTU 1532 (pppd automatically subtracts 8 from what's set in the UCI config), not 1500 - which is indeed a strange configuration, likely a misunderstanding.
Configuration:
config interface 'wan'
option proto 'pppoe'
option username 'xxxxxxxx@visayas.globelines.com.ph'
option password 'xxxxxxxx'
option peerdns '0'
list dns '8.8.8.8'
list dns '8.8.4.4'
option metric '80'
option mtu '1508'
option ipv6 'auto'
option device '@modem'
config interface 'modem'
option proto 'static'
option ipaddr '192.168.254.2'
option netmask '255.255.255.0'
option defaultroute '0'
option delegate '0'
option device 'wan'
option mtu '1508'
Interface MTU and addresses:
# ip a
...
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1512 qdisc fq_codel state UP group default qlen 1000
link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
inet6 fe80::xxxx:xxxx:xxxx:xxxx/64 scope link
valid_lft forever preferred_lft forever
...
7: wan@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1508 qdisc noqueue state UP group default qlen 1000
link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
inet 192.168.254.2/24 brd 192.168.254.255 scope global wan
valid_lft forever preferred_lft forever
inet6 fe80::xxxx:xxxx:xxxx:xxxx/64 scope link
valid_lft forever preferred_lft forever
...
105: pppoe-wan: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 3
link/ppp
inet 10.40.xxx.xxx peer 10.205.78.123/32 scope global pppoe-wan
valid_lft forever preferred_lft forever
inet6 2001:fd8:xxxx:xx:xxxx:xxxx:xxxx:xxxx/64 scope global dynamic noprefixroute
valid_lft 2591998sec preferred_lft 604798sec
inet6 fe80::xxxx:xxxx:xxxx:xxxx peer fe80::xxxx:xxxx:xxxx:xxxx/128 scope link
valid_lft forever preferred_lft forever
Yes it took several auto-retries to connect:
Tue Aug 30 13:45:46 2022 daemon.notice pppd[30310]: pppd 2.4.9 started by root, uid 0
Tue Aug 30 13:45:46 2022 daemon.debug pppd[30310]: Send PPPOE Discovery V1T1 PADI session 0x0 length 18
Tue Aug 30 13:45:46 2022 daemon.debug pppd[30310]: dst ff:ff:ff:ff:ff:ff src xx:xx:xx:xx:xx:xx
Tue Aug 30 13:45:46 2022 daemon.debug pppd[30310]: [service-name] [host-uniq 66 76 00 00] [PPP-max-payload 05 dc]
Tue Aug 30 13:45:50 2022 daemon.debug pppd[30310]: Recv PPPOE Discovery V1T1 PADT session 0x2167 length 0
Tue Aug 30 13:45:50 2022 daemon.debug pppd[30310]: dst xx:xx:xx:xx:xx:xx src xx:xx:xx:xx:xx:xx
Tue Aug 30 13:45:50 2022 daemon.debug pppd[30310]:
Tue Aug 30 13:45:51 2022 daemon.debug pppd[30310]: Send PPPOE Discovery V1T1 PADI session 0x0 length 18
Tue Aug 30 13:45:51 2022 daemon.debug pppd[30310]: dst ff:ff:ff:ff:ff:ff src xx:xx:xx:xx:xx:xx
Tue Aug 30 13:45:51 2022 daemon.debug pppd[30310]: [service-name] [host-uniq 66 76 00 00] [PPP-max-payload 05 dc]
Tue Aug 30 13:45:52 2022 daemon.debug pppd[30310]: Recv PPPOE Discovery V1T1 PADO session 0x0 length 67
Tue Aug 30 13:45:52 2022 daemon.debug pppd[30310]: dst xx:xx:xx:xx:xx:xx src xx:xx:xx:xx:xx:xx
Tue Aug 30 13:45:52 2022 daemon.debug pppd[30310]: [AC-name LHG_BNG-002] [host-uniq 66 76 00 00] [PPP-max-payload 05 dc] [service-name globelines] [service-name] [AC-cookie c9 99 76 dd 03 15 54 21 59 07 7d 7b 30 44 b8 b5]
Tue Aug 30 13:45:52 2022 daemon.debug pppd[30310]: Send PPPOE Discovery V1T1 PADR session 0x0 length 38
Tue Aug 30 13:45:52 2022 daemon.debug pppd[30310]: dst xx:xx:xx:xx:xx:xx src xx:xx:xx:xx:xx:xx
Tue Aug 30 13:45:52 2022 daemon.debug pppd[30310]: [service-name] [host-uniq 66 76 00 00] [PPP-max-payload 05 dc] [AC-cookie c9 99 76 dd 03 15 54 21 59 07 7d 7b 30 44 b8 b5]
Tue Aug 30 13:45:52 2022 daemon.debug pppd[30310]: Recv PPPOE Discovery V1T1 PADS session 0x3fa length 53
Tue Aug 30 13:45:52 2022 daemon.debug pppd[30310]: dst xx:xx:xx:xx:xx:xx src xx:xx:xx:xx:xx:xx
Tue Aug 30 13:45:52 2022 daemon.debug pppd[30310]: [service-name] [host-uniq 66 76 00 00] [PPP-max-payload 05 dc] [AC-name LHG_BNG-002] [AC-cookie c9 99 76 dd 03 15 54 21 59 07 7d 7b 30 44 b8 b5]
Tue Aug 30 13:45:52 2022 daemon.debug pppd[30310]: PADS: Service-Name: ''
Tue Aug 30 13:45:52 2022 daemon.info pppd[30310]: PPP session is 1018
Tue Aug 30 13:45:52 2022 daemon.warn pppd[30310]: Connected to xx:xx:xx:xx:xx:xx via interface wan