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Adrian Midgley wrote:
Is there a way to set up routing from here to a PC that has a fixed IP address when it is at its owner's university, and when it comes back here gets a different address?
Let's get clear - the routing is fine, you can route correctly to both IP addresses, you just have no way of knowing which is the right one. So what you have is a "name" problem not a routing problem. Layer 7 not layer 4. Theoretically you could try the simplistic two entries in the DNS. 18:05:38 srw srw $ dig test.eighth-layer.internal +short 192.168.0.2 192.168.0.1 In theory all well written applications will do something like this..... $ telnet test.eighth-layer.internal 25 Trying 192.168.0.2... telnet: connect to address 192.168.0.2: No route to host Trying 192.168.0.1... Connected to test.eighth-layer.internal. Escape character is '^]'. 220 wretched.demon.co.uk ESMTP For some definition of well written <urm RFC compliant surely - ed>, and of course half the time you have to wait for the wrong one to fail. Alternatively 'just' write a script that updates the DNS servers using nsupdate with the IP address DHCP returns. All it has to do is pass the IP address to something like this. A lot of magic happens in the background makin BIND 9 do dynamic DNS etc. 18:05:46 srw srw $ nsupdate -k ./dnskey/Ktest.+157+00995.private
update delete test.eighth-layer.internal.
18:09:07 srw srw $ nsupdate -k ./dnskey/Ktest.+157+00995.private
update add test.eighth-layer.internal. 10 A 192.168.0.2
In theory you should test return codes - etc etc - and you can probably find someone at comp.protocols.dns.bind who has done a few already. ifup calls scripts with variables set for IP address on most distros. It is a lot of work to avoid commenting and uncommenting one line - how many siblings do you have at University - or is this someone else? Much simpler would be to define names "laptophome" and "laptopuni" and change the name you use ;) Laptop home can be got from integrating DHCP and Dynamic DNS of course, if DHCP isn't handing out static IP addresses.
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