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ISDN connection problems?

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  • 24-07-2004 8:11pm
    #1
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    Registered Users Posts: 648 ✭✭✭


    Has anyone else around the country had connection problems with ISDN on the 1892 or 1893 numbers recently, especially outside the large cities?

    I've had two different relatives in the past two days with very similar problems: the PPP connections comes up correctly, Eircom's POP assigns an IP address to the PPP link, but attempts to send traffic down the link are rejected by the far end with an ICMP - Destination unreachable, from the Eircom POP address.

    If I try and ping the assigned IP address from a remote location (actually my own DSL link), I also get as far as the Eircom POP but no further.

    This seems to be intermittant, and is happening with assigned addresses in both the 159.134.* range and 213.94.* range (one location is in Wicklow, the other Mayo).

    Eircom support says no similar problems have been reported to them, but I'm confident this is not a local problem since both relatives were operating successfully up to a couple of days ago, and no changes have been made to any equipment.


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    #2
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    Registered Users Posts: 648 ✭✭✭Tenshot


    I'm confident this is not a local problem
    Well, maybe not quite so confident now...

    The problem turned out to be an issue with the DNS Proxy used in the ISDN router on each site. It was issuing DNS lookups with a source UDP port number of 1. This should really have been > 1024. Previously, Eircom's DNS server didn't care, but now, something in Eircom's network seems to be dropping such packets. I presume this is (a) a recent change and (b) not affecting every POP, since sometimes the packets still seem to get through.

    Changed the PCs to talk directly to the Eircom DNS server, and everything is now working again. (The routers in question are discontinued models, so unlikely to be getting new firmware any time soon.)


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