Router:Linux: Difference between revisions

== The Basics ==

You can use a Linux box in place of a PPPoE-capable router. Why would you want to do this?

* You're already running a Linux box, and you don't see any point in powering a router as well

* You want fine control over packets

* You have a PPPoE router but it doesn't do everything you want

== Debian/squeeze and /wheezy ==

This is what RogerBW is using. It'll probably be much the same on other Linuxen. The basic recipe came from [http://www.aa-asterisk.org.uk/index.php/Connecting_to_AAISP_using_PPPoE].

You will have two ethernet interfaces - one for your internal network (let's assume that's eth1), one for connection to the BT modem (eth0). You will be running PPPoE over the external interface, creating a new interface that actually passes packets.

=== Setup ===

* Install ppp, pppoe and iproute.

* Edit /etc/ppp/peers/aaisp to include:

<pre>

user mylogin@a.1 <----- your AAISP login

plugin rp-pppoe.so

eth0 <----- The ethernet interface to run PPPoE on

noipdefault

defaultroute

#usepeerdns <----- uncomment this if you want resolv.conf to be set up automatically

hide-password

lcp-echo-interval 1 <---- this is how often the LCP echo packets get sent to AAISP, in seconds.

lcp-echo-failure 10 <---- this is how many LCP echo failures before the ppp daemon quits

connect /bin/true

noauth

persist

maxfail 0 <---- redial forever until your modem regains sync else default is 10x or N times if you enter N

#holdoff 120 <---- this will cause pppd to dial once every 2 mins else default is 0 sec

mtu 1492

noaccomp

default-asyncmap

+ipv6

ipv6cp-use-ipaddr

</pre>

* Edit /etc/ppp/chap-secrets to include this line, consisting of three tab-separated words. The first entry is your AAISP router login, the second is an asterisk, and the third is your AAISP router password. For example:

<pre>

mylogin@a.1 * pa$$w0rd

</pre>

* Create /etc/ppp/ipv6-up.d/0000defaultroute. In it place the following shell script:

<pre>

#!/bin/bash

/sbin/ip -6 route add default dev $1

</pre>

* chmod it 755.

=== Testing ===

Run as root: pppoe -A

This should show something like this:

<pre>Access-Concentrator: BT_ADSL

Got a cookie: 6e c5 4a dd 1e c0 d6 b6 fe b4 4b 23 38 8f 63 58

AC-Ethernet-Address: 00:90:1a:40:f2:9f

--------------------------------------------------

</pre>

To start your PPPoE session just type

<pre>pon aaisp</pre>

and to stop it running

<pre>poff aaisp</pre>

You can check connectivity with a cron job, and add a stanza to /etc/network/interfaces to connect at boot.

=== Extra configuration ===

You will find at this point that most web sites work, but some few don't - they just freeze on loading or during initial SSL negotiation. This is because they are blocking ICMP, which is ''stupid'' - in part because they are then unable to indicate or respond to the need to fragment large packets. You can get round it by limiting the maximum packet size for TCP: set TCPfix on your clueless control panel, or on the router:

<pre>

iptables -t mangle -F FORWARD

iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1452

</pre>

== IPv6 ==

* Assign your /64 to the ''inside'' interface of your router - eth1 in this example.

<pre>

ifconfig eth1 inet6 add 2001:8b0:blah/64

</pre>

* Enable ipv6 forwarding by adding to /etc/sysctl.conf:

<pre>

net.ipv6.conf.default.forwarding=1

net.ipv6.conf.all.forwarding=1

</pre>

* If you don't want to reboot, also push these values into /proc/sys/etc.:

<pre>

echo 1 > /proc/sys/net/ipv6/conf/all/forwarding

echo 1 > /proc/sys/net/ipv6/conf/default/forwarding

</pre>

In theory, "default" should apply to all interfaces created later, while "all" should apply to all interfaces that exist now. This doesn't always seem to be the case.

== Full startup sequence ==

<pre>

ifconfig eth1 up

pon aaisp

</pre>

*IP-over-LCP patches (receive only):

**[https://sa.me.uk/pub/patches/linux/ip-over-lcp_2.6.35.4.patch 2.6.35.4]

**[https://sa.me.uk/pub/patches/linux/ip-over-lcp_3.2.0-rc5.patch 3.2.0-rc5]

== PPP Not coming back after a blip ==

This was reported in IRC on Feb 6th 2011. If you get people saying their line didn't come back or their linux box crashed (as in kernel oopsed) after a blip, turns out there's a bug in the kernel pppoe code for 2.6.36 which has been hitting me. some kind of double free in the disconnect code causes a kernel panic. there's a patch here: http://kerneltrap.org/mailarchive/linux-kernel/2010/12/3/4654538 which seems to work for me

[[Category:3rd Party Routers|Linux]]

=Also see=

[[Ebtables]]