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YaST allows you to specify a default router in the format that you used to configure an interface. This is fine for a leaf node in a simple network. However, if the network has more than one router, or you actually want to set up a router, you'll need need to specify a routing table. It can be done via Yast or by edition configuration files (which are overwritten by YAST).
There are two configuration files /etc/sysconfig/network/routes and /etc/sysconfig/network/ifroute-*.
The entries in the routing configuration files look like this:
DESTINATION GATEWAY NETMASK INTERFACE [ TYPE ] [ OPTIONS ] DESTINATION GATEWAY PREFIXLEN INTERFACE [ TYPE ] [ OPTIONS ] DESTINATION/PREFIXLEN GATEWAY - INTERFACE [ TYPE ] [ OPTIONS ]
To omit GATEWAY, NETMASK, PREFIXLEN, or INTERFACE, write - instead. The entries TYPE and OPTIONS may just be omitted.
The following scripts in the directory /etc/sysconfig/network/scripts/ assist with the handling of routes:
The first column specifies a destination. This can be either a network address, a host address, or the string default for the default gateway. Whether the given address is a host or a network is determined by the netmask given in the third column. The network mask for a host is always 255.255.255.255. Everything else specifies a network route. Network route means a route to a network, whereas a host route is a route to a single host.10.29.9.100 10.29.129.1 255.255.255.255 - 10.4.33.238 10.29.129.1 255.255.255.255 - 10.29.2.13 10.29.129.1 255.255.255.255 - 10.29.2.18 10.29.129.1 255.255.255.255 - 10.29.7.0 10.29.129.1 255.255.255.0 - 10.192.0.0 10.29.129.1 255.192.0.0 - default 10.29.129.3 - -
The second column gives either the IP address of the router, which should be used to reach the destination given in the first column, or the special value 0.0.0.0, which means that all traffic headed to the destination will be given to1 the device specified in the last column. If a gateway address is given, the device specification is optional.
The third column contains netmask.
Setting up static routing192.168.0.0 0.0.0.0 255.255.255.128 eth0 default 192.168.0.1
This routing table is typical for a simple network host. It could be any host in Network A from Figure 9-2. As you can see, comment lines start with a hash sign (#) in the first column. Comment lines and empty lines are ignored when the route script sets up the kernel routing table.
The other lines represent routing table entries. The format is very close to the output of the route command, as we demonstrate in Chapter 9.
The first column specifies a destination. This can be either a network address, a host address, or the string default for the default gateway. Whether the given address is a host or a network is determined by the netmask given in the third column. The network mask for a host is always 255.255.255.255. Everything else specifies a network route. Network route means a route to a network, whereas a host route is a route to a single host. The second column gives either the IP address of the router, which should be used to reach the destination given in the first column, or the special value 0.0.0.0, which means that all traffic headed to the destination will be given to1 the device specified in the last column. If a gateway address is given, the device specification is optional.
To clearly illustrate this, we refer back to Figure 9-2 and have a look at the entries of the routing tables of the hosts and routers in this network.
Hosts in Network A These hosts use the table shown above. They can reach the subnet 192.168.0.0/25 directly over their ethernet card, and send everything else to Router A/B at 192.168.0.1.
Hosts in Network B Here we have two routers, Router A/B for traffic to Network A, and Router B/C for everything else:# route to local subnet 'Network B' 192.168.0.128 0.0.0.0 255.255.255.128 eth0 # route to 'Network A' 192.168.0.0 192.168.0.130 255.255.255.128 # default gateway is 'Router B/C' default 192.168.0.129
This example illustrates a very important point. All router addresses must be within a network that can be reached directly through an interface of this machine. This seems to be pretty obvious, because how should a host send packages to a router if it is not in the same network segment? And yet, this is a common mistake that is made when one is setting up routing tables. The address used for Router A/B must be 192.168.0.130 and not 192.168.0.1, because the latter one is not part of this subnet.
Hosts in Network C Same situation as in Network A. One router gets all the traffic not destined to the local subnet:# route to local subnet 'Network C' 192.168.1.0 0.0.0.0 255.255.255.0 eth0 # default router is 'Router B/C'default 192.168.1.1
Router A/B This machine is directly connected to two subnets and forwards all traffic destined to Router B/C:# route to 'Network A' (local) 192.168.0.0 0.0.0.0 255.255.255.128 eth0 # route to 'Network B' (local) 192.168.0.128 0.0.0.0 255.255.255.128 eth1
# default gateway is 'Router B/C' default 192.168.0.129
Router B/C This machine is your connection to the Internet. We assume that it uses an ISDN link (which also is a point-to-point connection) to some router located at the ISP. As we stated previously, this router has the IP address 18.104.22.168. So besides setting up the routes for the local environment, you need to set up a route to this machine and then you can use this machine as the default gateway:# route to 'Network C' (local) 192.168.1.0 0.0.0.0 255.255.255.0 eth1 # route to 'Network B' (local) 192.168.0.128 0.0.0.0 255.255.255.128 eth0 # route to 'Network A' (via 'Router A/B') 192.168.0.0 192.168.0.130 255.255.255.128 # route to ISP router 22.214.171.124 0.0.0.0 255.255.255.255 isdn0 # default router is ISP's machine default 126.96.36.199
Again you can see that you first need a route to the default gateway before you can use it as a hop to other hosts. Because the ISDN connection is point-to-point, this route is a host route. The netmask for a route to a single host is 255.255.255.255, which means that all bits of the netmask are set. There are no bits left to distinguish between different hosts in this address because it points to only one machine.
The basic principle of routing is to forward packages not destined to a local subnet to another router which knows how handle them. The example shown doesn't reflect this strategy, that is, the hosts in Network B could send all packages that don't go to machines in the same subnet to Router B/C. This router knows that traffic for Network A has to go to Router A/B. So why do you need the extra entry in the routing table for Network A? Well, you don't really need it; the setup would work without it. As soon as a host from Network B sends packages for a host in Network A to Router B/C (you still know what's going on?), it would get an ICMP redirect from Router B/C that tells it to send those traffic directly to Router A/B.
I want SuSE to automatically remember some routes I always have to feed it when it restarts. How do I do that?
route add -net 188.8.131.52 gw 184.108.40.206 netmask 255.255.255.0 dev eth0
In MS DOS I can just "route add -p" for persistant. man route didn't help much (I loathe man pages - the way they are written is overly geeky and 87% of the time I haven't got a clue what they're on about. And they are so DULL to read).
Any help greatly appreciated!
[/b] Yast -> Network Devices -> Network card -> Edit -> Routing
You can also edit /etc/sysconfig/network/routes if you prefer the CLI.
SUSE 10 Setting up static route for two NICs same subnet suse, route, static, add
I have a machine I am using that has 2 NIC cards being used as a snort/ntop box. I use one NIC for listening to traffic and one for browsing the ntop reports and ACID reports. I have been able to get the computer up and running, performing beautifully, collecting data and giving reports. The problem I have run into comes from making these settings permanent after a reboot/power failure. With all the different distributions and most interest in IPChains for 2 NICs, I can't seem to find any relevant (to SUSE 10) articles on the Internet that show where I need to place the settings I need. I've looked in the /etc/sysconfig/network/ifc
fg* files and /etc/sysconfig/network/scr ipts but I can't seem to get my head around what to make changes to.
To get the following setup:
eth0 Link encap:Ethernet HWaddr 00:B0:D0:17:E4:8C
inet addr:172.16.26.178 Bcast:172.16.27.255 Mask:255.255.254.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
eth1 Link encap:Ethernet HWaddr 00:A0:CC:7C:07:33
inet addr:172.16.26.177 Bcast:172.16.27.255 Mask:255.255.254.0
UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
short.abc.com * 255.255.255.255 UH 0 0 0 eth0
172.16.26.0 * 255.255.254.0 U 0 0 0 eth0
172.16.26.0 * 255.255.254.0 U 0 0 0 eth0
link-local * 255.255.0.0 U 0 0 0 eth0
loopback * 255.0.0.0 U 0 0 0 lo
default 172.16.26.60 0.0.0.0 UG 0 0 0 eth0
the steps/commands I run to get this setup after a reboot are:
eth0 [E4:8C] (.178) Talk: nothing
1) Set eth1 [07:33] (.177) to listen (promisc): ifconfig eth1 promisc
2) remove the default eth1 subnet route: route del -net 172.16.26.0 netmask 255.255.254.0 eth1
3) add eth0 as host: route add -host 172.16.26.178 eth0
4) add route for subnet traffic to eth0: route add -net 172.16.26.0 netmask 255.255.254.0 eth0
5) add default gateway for all traffic: route add default gateway 172.16.26.60 eth0
Anyone know where the settings must be placed so that I don't have to go to the console and rekey the route commands? I know this should be easy, but I'm at a loss.
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