This article is a work in progress
Both modems should be set to Bridged Mode
Packages involved: pppd, shorewall, iproute2
/etc/ppp/peers/cat, configuration file for CAT Telecom provider:
noipdefault #defaultroute #replacedefaultroute #usepeerdns hide-password debug noauth persist maxfail 0 lcp-echo-interval 30 lcp-echo-failure 5 mtu 1492 plugin rp-pppoe.so eth0 rp_pppoe_service 'cat' user "lettersandnumbers@hinet.p" linkname cat unit 0
/etc/ppp/peers/tot, configuration file for TOT provider:
noipdefault #defaultroute #replacedefaultroute #usepeerdns hide-password debug noauth persist maxfail 0 lcp-echo-interval 30 lcp-echo-failure 5 mtu 1492 plugin rp-pppoe.so eth1 rp_pppoe_service 'tot' user "phoneno@totgoldbiz" linkname tot unit 1
I will explain the options.
#defaultroute #replacedefaultroute #usepeerdns
These we comment out, we will control default routes in the /etc/ppp/ip-up.local and /etc/ppp/ip-down.local scripts; we are not going to use DNS servers offered by the provider and will use fixed DNS (like Google DNS) instead.
persist maxfail 0 lcp-echo-interval 30 lcp-echo-failure 5
Persist sets pppd to keep the connection; maxfail 0 prevents pppd from giving up after 5 unsuccessful connections; we are sending line control protocol “pings” every 30 seconds and going to disconnect and try to connect back again if 5 of these “pings” are lost in a row.
unit 0 linkname cat
unit is a very important option to nail the number (ppp0, ppp1 etc.) of the connection. If this option is not specified, the connections will be numbered in the order they are established and the interface number would change all the time. linkname defines the name of .pid created in /var/run, I check for the existence of these files from PHP script to report in the web interface if the provider connection is on or off.
/etc/network/interfaces (fragment)
auto cat iface cat inet ppp pre-up /sbin/ifconfig eth0 up # line maintained by pppoeconf provider cat auto tot iface cat inet ppp pre-up /sbin/ifconfig eth1 up # line maintained by pppoeconf provider tot
/etc/iproute2/rt_tables
# # reserved values # 255 local 254 main 253 default 0 unspec # # local # 100 ppp0 200 ppp1
/etc/ppp/ip-up.local
#!/bin/bash
if [[ "$PPP_IFACE" == "ppp0" ]] ; then
METRIC=1
else
METRIC=2
fi
ip route add default dev $PPP_IFACE table $PPP_IFACE
ip route add default dev $PPP_IFACE metric $METRIC
ip rule add from $PPP_LOCAL lookup $PPP_IFACE
shorewall refresh
/usr/sbin/ddclient -syslog -file /etc/ddclient-$PPP_IFACE.conf
pppd does not have option to specify interface metric. There is a proposed patch for it, but it is not in the mainline yet. That’s why we move routing setup to this file. First line adds a default route to the routing table named ppp0 or ppp1. Third line adds a rule: if the source address of a packet is a local address of ppp interface, route it through this specific table (ppp0 or ppp1).
I am not sure if refreshing shorewall config is really needed, but won’t do any harm. ddclient updates DynDNS records using two different config files for two interfaces.
/etc/ppp/ip-down.local
#!/bin/sh ip route del default table $PPP_IFACE ip route del default dev $PPP_IFACE ip rule del lookup $PPP_IFACE shorewall refresh
/etc/shorewall/interfaces (fragment)
net ppp0 detect tcpflags,routefilter,nosmurfs,mss=1452 net ppp1 detect tcpflags,routefilter,nosmurfs,mss=1452
Important to clamp MSS to 1452 bytes here
“ip route show” output when both connections are on:
default dev ppp0 scope link metric 1 default dev ppp1 scope link metric 2
Primary interface ppp0, with lowest metric is used first. If it will go down, the second default route will be used automatically.
To be continued – from failover to load-balancing…