Chapter-1 How packets move on the local wire

Web Appendix-5 (RTERR) route command error messages

This appendix lists error messages from the route command for Linux and for Windows, explains what the messages mean, and suggests common causes and how to fix them.

Linux

Notes:

The Linux error messages are dreadful – they’re very unclear and unhelpful if you’re not used to them.
On Linux you can omit ‘metric n’ or the word ‘metric’, unlike other UNIX systems such as Solaris that insist on the metric parameter.
You can enter more than one route for exactly the same destination and netmask as long as each route has a different gateway. When you come to delete these routes, if there’s ambiguity, Linux deletes the first matching one. You can remove the ambiguity by specifying the gateway, to explicitly remove a specific route.
In the messages below:

SIODELRT is an error message DELeting a RouTe
SIOADDRT is an error message ADDing a RouTe.

SIOCADDRT: Network is unreachable

route add default gw 1.2.3.4

The routeraddr isn’t on a directly-connected network so this machine would be unable forward packets to it.

SIOCADDRT: File exists

You are adding a route that exists already.

SIOCADDRT: No such device

You omitted the gw keyword before the default gateway address, as in:

route add -net 10.2.2.76/24 10.1.1.22 wrong

SIOCDELRT No such process

You have tried to delete a route that doesn’t exist. List the routes with route –n and check the destaddr and netmask that you entered

SIOCADDRT: Operation not supported by device

route add -net 10.0.0.0/8 10.1.1.254 wrong

route add –net 172.23.24.128/25 wrong

You omitted "gw" before the routeraddr or omitted the gateway details completely:

route add -net 10.0.0.0/8 gw 10.1.1.254 correct

route add –net 172.23.24.128/25 gw 10.1.1.22 correct

SIOCADDRT: Operation not permitted

You are not running as user root.

SIOCADDRT: Invalid argument

route add -net 10.2.2.0 gw 10.1.1.254 wrong

route del -net 172.23.0.0 wrong

You omitted the netmask a.b.c.d or /numbits when adding / deleting a route to a network.

route add -net 10.2.2.0 netmask 255.255.255.0 gw 10.1.1.254 correct

route add -net 10.2.2.0/24 gw 10.1.1.254 correct

route del -net 172.23.0.0/16 correct

route del -net 172.23.0.0 netmask 255.255.0.0 correct

route: netmask doesn't match route address followed by "usage" message:

route add -net 10.7.8.9 netmask 255.0.0.0 gw 10.1.1.22 wrong
route add -net 10.2.2.76/24 gw 10.1.1.22 wrong

The destaddr isn’t a network address in the sense explained in BACKREF(Module 4.XXX) – it must be the lowest address in the range:

route add -net 10.0.0.0 netmask 255.0.0.0 gw 10.1.1.22 correct
route add -net 10.2.2.0/24 gw 10.1.1.22 correct

route: netmask 00ffffff doesn't make sense with host route followed by "usage" message:

route add 10.1.1.64/26 gw 10.1.1.254 wrong
route add 10.1.1.64 gw 10.1.1.254 netmask 255.255.255.192 wrong

Most likely: you omitted "-net" by mistake, when adding / deleting a route to a network:

route add -net 10.1.1.64/26 gw 10.1.1.254 correct
route add -net 10.1.1.64 gw 10.1.1.254 netmask 255.255.255.192 correct

Less likely: you wrongly inserted a netmask a.b.c.d or /numbits when defining a route to a single host:

route add 10.1.1.64 gw 10.1.1.254 correct

a.b.c.d.e Unknown host

route add -net 10.5.6.7.8/8 gw 10.1.1.254 wrong

route add default gw 1.2.3.4.5 wrong

You have entered a 5-byte destaddr by mistake, which can’t be correct.

addr: Host name lookup failure

route add -net 172.23.0.0 gw 10.1.1.254 netmask 255.255.255.25x wrong
route add -net 172.23.0.0 gw 10.1.1.254 netmask mars wrong

The netmask isn’t all numeric; route tries to look it up in the DNS to convert it to numeric, and fails.

addr: Unknown host

route add -net 172.23.0.0 gw 10.1.1.22 netmask 255.255.255.256 wrong

route add -net 172.23.0.0 gw 10.1.1.22 netmask 255.257.258.259 wrong

The netmask is numeric but isn’t a valid netmask causing route to misinterpret it

route: bogus netmask 255.255.255.25

route add -net 172.23.0.0 gw 10.1.1.22 netmask 255.225.0.0 wrong

route add -net 172.23.0.0 gw 10.1.1.22 netmask 10.1.1.254 wrong

The netmask is numeric but is invalid. You made a typo entering the netmask (e.g. "225" instead of "255), or entered a host address by mistake, or else you mixed up a destination address with the netmask spec.

route add -net 172.23.0.0 gw 10.1.1.22 netmask 255.255.0.0 correct

"usage" message:

route add -net 10.2.2.76 /24 gw 10.1.1.22 wrong

The usage message on its own usually means a syntax error of some kind, so that the command didn’t really make sense, irrespective of the IP address or other settings on this machine. Typical causes are including:

space after the "/" in a /numbits range spec, or space between the destaddr and the /numbits.
entering a field more than once (e.g. two netmasks or two destaddrs)

Warning: you can enter silly /numbits values when specifying a netmask. E.g. you can enter /45 which equates to /(45-32) = /13. However, route correctly notices that /38 … /33 are wrong.

Warning: The formats of route add and route del commands and of netstat -r output, are different on different variants of UNIX. (We have often found this confusing, and on Solaris created a point-to-point route inadvertently and wrongly.)

Windows

Notes:

If you forget to specify a netmask, your command defines a host route which is probably not what you wanted. E.g.

route add 0.0.0.0 10.1.2.3 wrong

doesn’t define a default gateway route. Instead it defines a route to the single host 0.0.0.0, i.e. with a netmask of 255.255.255.255

bad argument netmask

You typed the word netmask instead of mask

route add 0.0.0. mask 0.0.0.0 1.2.3.4 wrong

route delete 10.0.0.0 192.168.20.22 actually removed 10.0.0.0 192.168.20.99

xxx[14-Jun-01 finished here. steal unnecessary items from chap 3, and dup others. Check contents of table and the examples. Then do the "errors"

Problems:

The route addition failed: 87 - e.g. rout adde 10.6.7.0 mask 255.255.0.0. 10.2.2.2.222
but mask 255.255.255.0 is OK – not network address (lowest address in range)

or routeraddr not in a directly-connected range
Adding an extra default route in NT

bad destination address destaddr – maybe a name, or "default"

bad destination netmask address : what gave this

you can have silly netmask: route add 5.0.0.0 mask 255.255.255.256 10.2.2.222 = N-256

Also mask bytes less than 255 (but you might content that’s acceptable – because of variable length masks)

Win: How you can change your defgwy without rebooting. Gateway field is different from other IP params – not specific to NIC

findout(does manual default gateway change persist across reboots?)

using the route add metric in NT

whereputXXX[route add 0.0.0.0 MASK 0.0.0.0 <my local ip address>

Thus, packets destined for "non-local" subnets will be transmitted directly onto the local media instead of being sent to a router. In essence, the local interface card can be designated as the default gateway. This might be useful where several class "C" networks are being used on one physical network with no router to the outside world. ]

The route addition failed: 87 (from "route add" command)

The IP address you specified as the default gateway isn’t in the address range directly-connected to this machine, as specified by this machine’s IP address and netmask. E.g. if this is 10.1.1.59 netmask 255.255.255.0 the gateway address must be in the range
10.1.1.0 – 10.1.1.255

(This message could also mean that you don’t have the necessary privileges to add a route.)

(help message printed) (from "route add"command)

You’ve made a mistake in the command syntax. Typical causes are typing "del" instead of "delete", or omitting the gateway IP address, as in

route add 0.0.0.0 mask 0.0.0.0

Win: if you have an impossible gateway entered via Control Panel > Network may not be able to use route command properly – even commands with correct syntax don’t work, with message "no such route" or something. Recreate on timepc.

Notes and further reading

The route addition failed: 87

bibref(MS-KB Q151795) – not network address (lowest in range) or gateway address not on a network directly-connected to this machine

bibref(MS-KB Q163107) – need administrator privilege