MTU ppp interface

PPPoE related questions
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sibi1979
Posts: 7
Joined: 26 Jun 2017, 05:53

MTU ppp interface

Post by sibi1979 »

Dear accel-ppp lovers,

We are using the accel-ppp server as a l2tp and pppoe server.
We've seen that the ppp interface is each time created with an mtu of 1420.

Here are the ppp settings :
[ppp]
verbose=1
min-mtu=1280
mtu=1492
mru=1492

ppp33: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1420
inet X.X.X.X netmask 255.255.255.255 destination X.X.X.X
ppp txqueuelen 3 (Point-to-Point Protocol)
RX packets 666792 bytes 44302682 (42.2 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 673702 bytes 35547495 (33.9 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

How can we increase the mtu size to 1492 ? Why it is "negotiated" to 1420 ?

Thanks a lot for your support,

Sibi
Dmitry
Администратор
Posts: 954
Joined: 09 Oct 2014, 10:06

Re: MTU ppp interface

Post by Dmitry »

hi
show connection negotiation log
sibi1979
Posts: 7
Joined: 26 Jun 2017, 05:53

Re: MTU ppp interface

Post by sibi1979 »

Hey Dmitry,

root@bras:/var/log/accel-ppp# accel-cmd show connection negotation log
command unknown

What is the correct commando please ? Do I have to enable something in the configuration file ?

By the way, how can we see all syntax of the "accel-cmd" ?

Thank you,

Sibi
Dmitry
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Posts: 954
Joined: 09 Oct 2014, 10:06

Re: MTU ppp interface

Post by Dmitry »

[ppp]
verbose=1

[log]
level=5

make connection and copy here /var/log/accel-ppp/accel-ppp.log
sibi1979
Posts: 7
Joined: 26 Jun 2017, 05:53

Re: MTU ppp interface

Post by sibi1979 »

Thanks Dmitry.
At this moment, log level is at 3. I have set it to 5.
As the server is in production, is there a possibility to reload the config without loosing the existing sessions ?
Dmitry
Администратор
Posts: 954
Joined: 09 Oct 2014, 10:06

Re: MTU ppp interface

Post by Dmitry »

yes, use accel-cmd reload
sibi1979
Posts: 7
Joined: 26 Jun 2017, 05:53

Re: MTU ppp interface

Post by sibi1979 »

Please find hereunder the extented log.


[2017-12-01 13:29:41]: debug: ppp17: recv [LCP EchoReq id=db <magic b3d1ef55>]
[2017-12-01 13:29:41]: debug: ppp17: send [LCP EchoRep id=db <magic 12200854>]
[2017-12-01 13:29:41]: info: : recv [LCP ConfReq id=1c <mru 1420> <magic b4509cef>]
[2017-12-01 13:29:41]: info: : send [LCP ConfAck id=1c ]
[2017-12-01 13:29:41]: debug: : lcp_layer_started
[2017-12-01 13:29:41]: debug: : auth_layer_start
[2017-12-01 13:29:41]: info: : send [CHAP Challenge id=1 <eef3c4f96fe4ab7d84f43aec459d84>]
[2017-12-01 13:29:41]: info: : recv [CHAP Response id=1 <35685f63dee7df4525ebe5e512d4b2cf>, name="yyy_doctor_fix@xxxx"]
[2017-12-01 13:29:41]: debug: : radius(1): req_enter 1
[2017-12-01 13:29:41]: info: : send [RADIUS(1) Access-Request id=1 <User-Name "yyy_doctor_fix@xxxx"> <NAS-Identifier "nao-bras"> <NAS-IP-Address 10.50.201.x> <NAS-Port-Type Virtual> <Service-Type Framed-User> <Framed-Protocol PPP> <Calling-Station-Id "x.x.x.x"> <Called-Station-Id "x.x.x.x"> <CHAP-Challenge > <CHAP-Password >]
[2017-12-01 13:29:41]: debug: : radius(1): req_exit 0
[2017-12-01 13:29:41]: info: : recv [RADIUS(1) Access-Accept id=1 <Framed-Protocol PPP> <Framed-Compression Van-Jacobson-TCP-IP> <Framed-IP-Address x.x.x.x>]
[2017-12-01 13:29:41]: info: ppp35: connect: ppp35 <--> l2tp( x.x.x.x:1701 session 18605-33779, 3630-9558)
[2017-12-01 13:29:41]: debug: ppp35: ppp connected
[2017-12-01 13:29:41]: info: ppp35: send [CHAP Success id=1 "Authentication succeeded"]
[2017-12-01 13:29:41]: debug: ppp35: auth_layer_started
[2017-12-01 13:29:41]: debug: ppp35: ccp_layer_start
[2017-12-01 13:29:41]: debug: ppp35: ipcp_layer_start
[2017-12-01 13:29:41]: info: ppp35: send [IPCP ConfReq id=1 <addr x.x.x.x>]
[2017-12-01 13:29:41]: debug: ppp35: ipv6cp_layer_start
[2017-12-01 13:29:41]: info: ppp35: yyy_doctor_fix@xxx: authentication succeeded
[2017-12-01 13:29:41]: debug: ppp29: recv [LCP EchoReq id=fb <magic b3f41e04>]
[2017-12-01 13:29:41]: debug: ppp29: send [LCP EchoRep id=fb <magic 1befd79f>]
[2017-12-01 13:29:41]: info: ppp35: recv [IPCP ConfReq id=1d <addr 0.0.0.0> <dns1 0.0.0.0> <dns2 0.0.0.0>]
[2017-12-01 13:29:41]: info: ppp35: send [IPCP ConfNak id=1d <addr x.x.x.x> <dns
Dmitry
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Posts: 954
Joined: 09 Oct 2014, 10:06

Re: MTU ppp interface

Post by Dmitry »

[l2tp]
ppp-max-mtu=1454

note, 1492 is too much for l2tp
sibi1979
Posts: 7
Joined: 26 Jun 2017, 05:53

Re: MTU ppp interface

Post by sibi1979 »

Thanks - the MTU of the ppp interface is now 1454, after the implementation of this parameter.
So this mean, in combination with l2tp, that we reached the maximum mtu ?
Dmitry
Администратор
Posts: 954
Joined: 09 Oct 2014, 10:06

Re: MTU ppp interface

Post by Dmitry »

yes
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