Ascend Pipeline 50 ISDN routers were configured by default to proxy-arp for all addresses they thought were on the internet side, presumably to save you having to enter a router address into all the local clients. (DHCP-capable clients might not have been ubiquitous at that point.)
Unfortunately this meant that if you plugged it into a physical network with hosts that disagreed with the P50 about what IP network they were on, for instance if you plugged it into the office network while configuring it for a customer's intended settings, it would use ARP to advertise itself as the right target for all your local IP addresses. Any host that was slower than the P50 would therefore become inaccessible as everything tried to send all the traffic for it to the P50 instead.
Our Windows boxes crashed in short order when this happened! Turn off or unplug the P50, e.g. because you'd finished setting it up, and everything started behaving again, at least until the next one. Took us quite a few before we realized what was going on.
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Date: 2008-11-13 02:18 pm (UTC)My favourite networking bug:
Ascend Pipeline 50 ISDN routers were configured by default to proxy-arp for all addresses they thought were on the internet side, presumably to save you having to enter a router address into all the local clients. (DHCP-capable clients might not have been ubiquitous at that point.)
Unfortunately this meant that if you plugged it into a physical network with hosts that disagreed with the P50 about what IP network they were on, for instance if you plugged it into the office network while configuring it for a customer's intended settings, it would use ARP to advertise itself as the right target for all your local IP addresses. Any host that was slower than the P50 would therefore become inaccessible as everything tried to send all the traffic for it to the P50 instead.
Our Windows boxes crashed in short order when this happened! Turn off or unplug the P50, e.g. because you'd finished setting it up, and everything started behaving again, at least until the next one. Took us quite a few before we realized what was going on.