hello everybody,

i've got a very strange problem:
enviroment

two sites

site A: NW6, SP3, BM3.7 SP2, setup with a dmz,
192.168.110.0/255.255.0.0,
router inside (dmzA) for ipsec, static nat publicA->dmzA

site B: NW5, SP6, BM3.6 SP2a, setup with a dmz,
192.168.120.0/255.255.0.0,
router inside (dmzB) for ipsec, static nat publicB->dmzB

set filters for ipsec and ping in/out.

between the two routers we've established an ipsec connection,
supplier
says it works.

for backup-reasons there should be an isdn-backup-line.
for checking the presence of the other site the public adresses of the

opposite sites are pinged.

although the appropriate filters are set pinging is very strange:
- if ping is possible (without any changes: not every time it will) it

will make only approx 20 pings then it stopps (regardless from the
router
or a ws)
- after a period of "recovery" (10-20 min) it might be possible again,
but
only for approx 20 pings ....
- this effect is not located in the routers since i placed a w2k ws in

this dmz's a the effect is the same (doublechecked all ip-settings,
mask,
gw ...)
- during this time a can ping the public addresses on all site vice
versa
from the border managers and they are alive


has got anybody any idea ?