🚀 go-pugleaf

In article <1992May12.155136.13843@news.acns.nwu.edu> owings@nwu.edu (Peter W. Owings) writes:
>
>I am wondering if anyone has tried to use IPTUNNEL across a WAN.

Yes, lots of people. There is one thing you should watch out for though.
When IP routers carry a datagram across an IP internetwork, each router
has to ARP the next hop (router) in order to send the datagram there.
Once an IP node has ARP'd another to determine its hardware address, the
IP address to hardware address mapping sits in a table called the ARP
cache. In that table, the entry will age while it is not being referenced
and, if it is not referenced for some implementation specific interval,
the entry will be discarded. When ARP is called into play by IP because
a mapping it needs is not in the ARP cache, most IP implementations
discard the datagram that "caused" the ARP, assuming that upper layer
protocols will eventually get around to retransmitting.

With the IP tunnel in NetWare 3.11, each IPX packet is carried across
the IP internet in a UDP datagram. NetWare uses watchdog packets to
intermitantly enquire whether remote entities (typically workstations)
are still there. If the watchdog packets have to traverse the tunnel
then it is possible that these packets may not have sufficient frequency
to prevent the ARP cache in a router somewhere along the IP route
from ageing out the next hop, causing it to drop the packet. So, the
watchdog packet never makes it to its destination, the destination
obviously does not respond and an incorrect decision is made regarding
the "upness" of a connection and it is cleared.

In reality, such a situation is rare but if you do experience intermitant
lossages of idle connections, you can increase the frequency of
the watchdog packets using a number of "set" commands at the server
console to keep the IP route humming at all times.

Keith
-
Keith Brown                                      Phone: (408) 473 8308
Novell San Jose Development Centre               Fax:   (408) 433 0775
2180 Fortune Dr, San Jose, California 95131      Net:   keith@novell.COM