arp -s question - help appreciated

arp -s question - help appreciated

Post by Steve Bellen » Wed, 12 Jul 2000 04:00:00



likely /etc/nsswitch.conf is doing something like
hosts:      nis [NOTFOUND=return] files
Which will only look at files when nis is down.

you could change it to `files nis' which will always look in files first
or perhaps change your arp request to an ip



>I can't find any info and MAN doesn't expand on this.  I'm trying to
>setup PPP dial-in with static addresses.

>/etc/hosts
>127.0 0.1
>146.82.25.158       myserver
>192.168.0.2 ppp_server
>192.168.0.3 ppp_client

>myserver ether address: 00:08:c7:8c:b4:d6

>Two different sets of instructions say to turn on IP forwarding and to
>execute:  
>    arp -s ppp_client 00:08:c7:8c:b4:d6 pub

>so that this system responds  to  ARP requests for ppp_client even
>though the hostname is not its own, but that always returns error:

>    ppp_client: No such device or address

>What am I not doing right?  Thanks for your responses.

>-AC

--
http://www.math.fsu.edu/~bellenot
bellenot <At/> math.fsu.edu
+1.850.644.7189 (4053fax)
 
 
 

arp -s question - help appreciated

Post by Steve Bellen » Wed, 12 Jul 2000 04:00:00


Hmmm... what does truss say?

truss -f -o /tmp/truss.out arp -s ppp_client 00:08:c7:8c:b4:d6 pub



>Thanks, hosts is set up with only "files dns."  I also tried the IP
>only with the same error message.  I've also tried it on a freshly
>installed system - same thing..

>-AC



>>likely /etc/nsswitch.conf is doing something like
>>hosts:      nis [NOTFOUND=return] files
>>Which will only look at files when nis is down.

>>you could change it to `files nis' which will always look in files first
>>or perhaps change your arp request to an ip



>>>I can't find any info and MAN doesn't expand on this.  I'm trying to
>>>setup PPP dial-in with static addresses.

>>>/etc/hosts
>>>127.0 0.1
>>>146.82.25.158       myserver
>>>192.168.0.2 ppp_server
>>>192.168.0.3 ppp_client

>>>myserver ether address: 00:08:c7:8c:b4:d6

>>>Two different sets of instructions say to turn on IP forwarding and to
>>>execute:  
>>>    arp -s ppp_client 00:08:c7:8c:b4:d6 pub

>>>so that this system responds  to  ARP requests for ppp_client even
>>>though the hostname is not its own, but that always returns error:

>>>    ppp_client: No such device or address

>>>What am I not doing right?  Thanks for your responses.

>>>-AC

--
http://www.math.fsu.edu/~bellenot
bellenot <At/> math.fsu.edu
+1.850.644.7189 (4053fax)

 
 
 

arp -s question - help appreciated

Post by Greg Andre » Thu, 13 Jul 2000 04:00:00



>I can't find any info and MAN doesn't expand on this.  I'm trying to
>setup PPP dial-in with static addresses.

>/etc/hosts
>127.0 0.1
>146.82.25.158       myserver
>192.168.0.2 ppp_server
>192.168.0.3 ppp_client

>myserver ether address: 00:08:c7:8c:b4:d6

>Two different sets of instructions say to turn on IP forwarding and to
>execute:  
>    arp -s ppp_client 00:08:c7:8c:b4:d6 pub

>so that this system responds  to  ARP requests for ppp_client even
>though the hostname is not its own, but that always returns error:

>    ppp_client: No such device or address

>What am I not doing right?  

You seem to be giving your PPP client an IP address that doesn't
exist on your Ethernet network.  Instead of giving the PPP client
an IP address in the 146.82.25.0 network, you're giving it an address
in the 192.168.0.0 network.

Even after you get the arp command to take your arguments, it doesn't
look like it'll work.  Why not?  Because the other machines on your
Ethernet won't arp for 192.168.0.0 addresses.  They'll only arp for
146.82.25.0 addresses.  When those hosts try to reply to a 192.168.0.x
address, they'll send the packets to the default router, which will
probably pass them to its default route, probably out to the Internet
rather than to your PPP server.

That's probably why the arp command is barfing on your hostname.
192.168.0.3 is not a valid address on your ethernet interface.

Give the PPP client an unused IP address in the block of addresses
that are on your ethernet segment, and use that in your arp command.

You don't need a special IP address for your PPP server.  PPP can use
the IP address on the Ethernet interface without any trouble.

  -Greg
--

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1. arp question - "arp who-has" problem

hi

i have a simple test network as follows:

----------   -------         -------   ----------
|        |   |     |---------|     |   |        |
| host 1 |---| rt1 |         | rt2 |---| host 2 |
|        |   |     |---------|     |   |        |
----------   -------         -------   ----------
.27.2         .27.1            .28.1      .28.2
              .15.1            .15.3
              .15.2            .15.4

The machines rt1 and rt2 are routers with 3 interfaces each: 1 to the
local subnet (either 27.0/24 or .28.0/24) and 2 interfaces on the .15.0/24
network (the 2 interfaces on .15.0/24 are necessary since this will
eventually be a load-balancing problem). The 6 interfaces on the 2 routers
plug into 1 hub. host 1 is connected to rt 1 via a crossover cable. A
crossover is also used between host 2 and rt 2.

What i'm trying to do is use a machine on one subnet to ping a machine on
a different subnet, and this doesnt work. eg. I cant use host 2 to ping
rt1 or host 1 to ping host 2. But all machines on the same subnet can
communicate just fine eg. rt2 and host2 can ping one another, and rt1 and
rt2 can ping one another.

The following is an example of the problem i'm having. I use rt1 to ping
host 2. When i do, rt2 gets the following message:

        arp who-has 146.141.28.2 tell 146.141.15.1

I know what this means, but i dont know how to send the hardware address
across to 146.141.15.1. Do i need proxy-arp or some sort of arp
forwarding??? Or should I be doing something completely different?

I just dont know where to start when fixing this problem. Pointers to
documentation are more than welcome.

Thanks in advance

kodge
fali at cs.wits.ac.za

NB: this is the network setup I have to use. i'm not in a position to
change it even if I wanted to.

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