Linux下如何实现双adsl链路冗余互备及流量分担？

Linux下如何实现双adsl链路冗余互备及流量分担？ - 乐维UP

Linux下如何实现双adsl链路冗余互备及流量分担？

 

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王新培，碧海蓝天一只鹰

我希望实现这些功能: 双adsl同时连线; 当两条adsl同时连线时,流量经策略路由分流到两条链路上; 当其中一条adsl掉线时,所有流量自动分配另一条可用连接; 可以扩展到多条ppp连接.请教如何实现？

Linux
网络管理
网络 (Networking)
流量
ADSL

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2012年02月27日

 
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王新培，碧海蓝天一只鹰

1.添加网卡
插入网卡，启动机器，修改/etc/modules.conf并加入
alias eth2 driver.o

2.配置adsl拨号
通过adsl-setup程序创建ppp0和ppp1的拨号配置文件，并保存配置。
修改/etc/sysconfig/network-scripts/ifcfg-ppp文件，将其中的PIDFILE参数设为：
PIDFILE=/var/run/ppp-adsl.pid
其中*对应0、1等
如果不修改此参数将无法启动第二个ppp接口。

3.启动ppp接口
因为adsl-start 命令缺省只能启动第一的ppp接口。所以要启动两个接口，必须指定配置文件。
adsl-start /etc/sysconfig/network-scripts/ifcfg-ppp0
adsl-start /etc/sysconfig/network-scripts/ifcfg-ppp1

4.添加路由表
缺省情况下，系统只有3个路由表，local、main、default，路由规则为所有进入的数据报都参照main、defaul来决策路由，这可以通过ip rule ls来查看。其输出如下：
[root@linuxrouter root]# ip rule ls

0: from all lookup local

32766: from all lookup main

32767: from all lookup 253

[root@linuxrouter root]#

要实现策略路由，添加额外的路由表是必须的。
下面两条命令分别添加名为ppp0和ppp1的路由表。

echo 201 ppp0 >;>; /etc/iproutes/rt_tables
echo 202 ppp1 >;>; /etc/iproutes/rt_tables

5.创建路由表项
上面创建的两个路由表都是空表，需要在其中注入路由表项。
本人编写了如下脚本用于注入路由表项：

!/bin/bash

Name: cprt

This program copy the route from $1 route table to $2 route table,

exclude the default route entry.

if [ -z "$1" -o -z "$2" ]; then

echo $"usage: cprt <source_table>; <dest_table>;"

exit 1

fi

SOURCE=$1

DEST=$2

Clear the destination route table

echo $"Clearing route table $DEST ......"

echo

/sbin/ip route flush table $DEST

Inject routes from source to destination

echo $"Injecting route from $SOURCE to $DEST ......"

/sbin/ip route ls table $SOURCE | grep -v default >; /tmp/route-tmp

while read line; do

  /sbin/ip route add table $DEST $line

done < "/tmp/route-tmp"

把main表中的路由表项复制到ppp0和ppp1中。
将下面命令加入到/etc/rc.d/rc.local中。
cprt main ppp0
cprt main ppp1

此时，两个路由表中都有相同的路由表项了，除了default路由以外。缺省路由的添加要通过另外的途径添加。当ppp激活，或者掉线时，pppd守护进程会调用/etc/ppp/目录下的ip-up、ip-down脚本，这些教本又分别调用ip-up.local、ip-down.local。在此我们利用这两个脚本来对路由表和流量控制策略进行维护，此脚本需要人工创建。

下面时本例中的脚本：
/etc/ppp/ip-up.local

!/bin/bash

Name: ip-up.local

Created by lyking@CU

If the if-down is not completed, this script can't be excute.

while [ -e /var/lock/subsys/if-down.$IFNAME ] ; do

    sleep 3

done

Creat a lock file to prevent the if-down from running on my turn

touch /var/lock/subsys/if-up.$IFNAME

Determin device here

We should use IFNAME as the interface name.For some reason, the IFNAME maybe not

same as the LINKNAME. And the route table should associate with the IFNAME. For

some conveniency, I name the route table as "ppp0" and "ppp1".

RT_TABLE=$IFNAME

Add or change static route here,including default route.

Check if a default is exist.

RS=""

ip route ls table $RT_TABLE | grep default

RS=$?

if [ $RS -eq 0 ] ; then

    ip route change default dev $IFNAME table $RT_TABLE

else

    ip route add default dev $IFNAME table $RT_TABLE

fi

echo >;>; /var/log/ifchang.log

echo "$0: $IFNAME going up at date." >;>; /var/log/ifchang.log

echo "$0: $IFNAME got address: $IPLOCAL, peer address is $IPREMOTE." >;>; /var/log/ifchang.log

echo "$0: Table $RT_TABLE default route change to ip route ls table $RT_TABLE | grep default." >;>; /var/log/ifchang.log

Refresh routing cache to activating the routing immediately.

ip route flush cache

Add traffic control policy here

tc qdisc add dev $IFNAME root handle 1: prio

This instantly creates classes 1:1, 1:2, 1:3

tc qdisc add dev $IFNAME parent 1:1 handle 10 sfq perturb 20

tc qdisc add dev $IFNAME parent 1:2 handle 20 sfq perturb 20

tc qdisc add dev $IFNAME parent 1:3 handle 30 sfq

Remove the lock file

rm -f /var/lock/subsys/if-up.$IFNAME

/etc/ppp/ip-down.local

!/bin/bash

Name: ip-down.local

Created by lyking@CU

while [ -e /var/lock/subsys/if-up.$IFNAME ] ; do

    sleep 3

done

touch /var/lock/subsys/if-down.$IFNAME

cd /etc/sysconfig/network-scripts

. network-functions

Determin device here

We should use IFNAME as the interface name.For some reason, the IFNAME maybe not

same as the LINKNAME. And the route table should associate with the IFNAME. For

some conveniency, I name the route table as "ppp0" and "ppp1".

RT_TABLE=$IFNAME

Looking for a valide connection to Internet

DEFAULT_RT=""

PPPS='ppp0 ppp1'

for i in $PPPS ; do

ifconfig | grep $i

RS=$?

    if [ $RS -eq 0 ] ; then

        DEFAULT_RT=$i

        break

    fi

done

Update default route here as nesessary

if [ $DEFAULT_RT != $IFNAME ] ; then

    if [ $DEFAULT_RT != "" ] ; then

            ip route add default dev $DEFAULT_RT table $RT_TABLE

    else

            for i in $PPPS ; do

                    ip route del default dev $i table $i

            done

            echo >;>; /var/log/ifchang.log

            echo "$0: All connection is down, remove all default route from all branch tables" >;>; /var/log/ifchang.log

    fi

    echo >;>; /var/log/ifchang.log

    echo "$0: $IFNAME going down at `date`." >;>; /var/log/ifchang.log

    echo "$0: Connection lasted $CONNECT_TIME seconds." >;>; /var/log/ifchang.log

    echo "$0: $BYTES_SENT bytes sent, $BYTES_RCVD bytes received." >;>; /var/log/ifchang.log

    echo "$0: $DEFAULT_RT is available." >;>; /var/log/ifchang.log

    echo "$0: Table $RT_TABLE default route changed to `ip route ls table $RT_TABLE | grep default`. " >;>; /var/log/ifchang.log

fi

Refresh routing cache to activating the routing immediately.

ip route flush cache

rm -f /var/lock/subsys/if-down.$IFNAME

注意，创建完脚本后必须将其属性改为可执行，否则不会被执行。

6.路由策略的选择
策略路由可以通过源地址、目标地址、ToS或者fwmark标记来进行选择。在此，为了利用iptables的强大的过滤功能采用fwmark标记来决策路由。
在/etc/rc.d/rc.local中添加如下命令：
/sbin/ip rule add fwmark 1 table ppp0
/sbin/ip rule add fwmark 2 table ppp1

7.防火墙规则的添加
这里利用的iptables的强大过滤功能来对流量进行标记。本例中仅根据ip地址的奇偶性来拆分流量，根据具体需求，你还可以根据第4层端口号、ToS等来拆分流量。防火墙需要添加如下命令：

Divid traffic to different mark

iptables -t mangle -A PREROUTING -s 10.0.0.0/255.255.255.1 -j MARK --set-mark 0x1

iptables -t mangle -A PREROUTING -s 10.0.0.1/255.255.255.1 -j MARK --set-mark 0x2

NAT

/sbin/iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE

/sbin/iptables -t nat -A POSTROUTING -o ppp1 -j MASQUERADE

至此，双adsl链路的热互备及负载分担基本完成。

下面是一些运行结果
A.ifconfig显示结果
ppp0 Link encap:Point-to-Point Protocol

      inet addr:220.163.38.208  P-t-P:220.163.38.1  Mask:255.255.255.255

      UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1492  Metric:1

      RX packets:100295 errors:0 dropped:0 overruns:0 frame:0

      TX packets:67817 errors:0 dropped:0 overruns:0 carrier:0

      collisions:0 txqueuelen:3

      RX bytes:108844271 (103.8 Mb)  TX bytes:6073206 (5.7 Mb)

ppp1 Link encap:Point-to-Point Protocol

      inet addr:220.163.36.57  P-t-P:220.163.36.1  Mask:255.255.255.255

      UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1492  Metric:1

      RX packets:150583 errors:0 dropped:0 overruns:0 frame:0

      TX packets:125136 errors:0 dropped:0 overruns:0 carrier:0

      collisions:0 txqueuelen:3

      RX bytes:132921157 (126.7 Mb)  TX bytes:8749585 (8.3 Mb)

B./var/log/ifchang.log部分内容
/etc/ppp/ip-down.local: ppp0 going down at Tue Aug 10 08:05:45 CST 2004.
/etc/ppp/ip-down.local: Connection lasted 22 seconds.
/etc/ppp/ip-down.local: 30 bytes sent, 30 bytes received.
/etc/ppp/ip-down.local: ppp1 is available.
/etc/ppp/ip-down.local: Table ppp0 default route changed to default dev ppp1 scope link .

/etc/ppp/ip-up.local: ppp0 going up at Tue Aug 10 08:05:53 CST 2004.
/etc/ppp/ip-up.local: ppp0 got address: 61.159.254.30, peer address is 61.159.254.1.
/etc/ppp/ip-up.local: Table ppp0 default route change to default dev ppp0 scope link .

/etc/ppp/ip-down.local: ppp1 going down at Tue Aug 10 08:12:45 CST 2004.
/etc/ppp/ip-down.local: Connection lasted 853 seconds.
/etc/ppp/ip-down.local: 9313 bytes sent, 116181 bytes received.
/etc/ppp/ip-down.local: ppp0 is available.
/etc/ppp/ip-down.local: Table ppp1 default route changed to default dev ppp0 scope link .

/etc/ppp/ip-up.local: ppp1 going up at Tue Aug 10 08:12:53 CST 2004.
/etc/ppp/ip-up.local: ppp1 got address: 220.163.38.20, peer address is 220.163.38.1.
/etc/ppp/ip-up.local: Table ppp1 default route change to default dev ppp1 scope link .[list=][/list][list][/list]