Podivna vec s default gw

[Borek Lupomesky]

   Hi all,

   Prisel jsem na velmi divnou vec v IP vrstve, kterou nechapu:
   Mam dva pocitace propojene ethernetem s adresami 192.168.0.1/24 a
192.168.0.2/24. IP provoz mezi nimi je bez problemu. Na prvnim stroji
(.1) provedu akci:

   # route add default gw 192.168.0.2

   Od teto chvile prestane sit fungovat. Ping z .1 na .2
nefunguje (ani naopak). Pritom kdyz se podivam na ethernet pres tcpdump,
tak vidim jak ICMP request tak ICMP reply prichazejici z .2. Evidentne
ty pakety zahazuje samotny Linux.
   A mozna, ze je ani nezahazuje -- pokud totiz pustim ping a v jeho
prubehu pridam default route a po par vterinach zase odeberu, tak ty
pingy se neztrati, ale najednou -- v jednom zatahu se vyhrnou s
prislusnym zpozdenim (viz vypis nize).
   Chape nekdo, co se deje? Podrobnejsi udaje jsou na konci mailu.

   Bye Borek

-=-=-8<-=-=-=-
Distribuce: RH 6.2
Verze kernelu: 2.2.16
Routovaci tabulka:

diaspar:~# route -n
Kernel IP routing table
Destination   Gateway       Genmask         Flags Metric Ref    Use If
192.168.0.1   0.0.0.0       255.255.255.255 UH    0      0        0 eth0
192.168.0.0   0.0.0.0       255.255.255.0   U     0      0        0 eth0
127.0.0.0     0.0.0.0       255.0.0.0       U     0      0        0 lo
0.0.0.0       192.168.0.2   0.0.0.0         UG    0      0        0 eth0

Ping behem ktereho je na par (zde cca 14) vterin nahozena default gw:

64 bytes from 192.168.0.2: icmp_seq=23 ttl=128 time=0.8 ms
64 bytes from 192.168.0.2: icmp_seq=24 ttl=128 time=0.8 ms
64 bytes from 192.168.0.2: icmp_seq=25 ttl=128 time=14000.3 ms
64 bytes from 192.168.0.2: icmp_seq=26 ttl=128 time=13001.1 ms
64 bytes from 192.168.0.2: icmp_seq=27 ttl=128 time=12001.6 ms
64 bytes from 192.168.0.2: icmp_seq=28 ttl=128 time=11002.1 ms
64 bytes from 192.168.0.2: icmp_seq=29 ttl=128 time=10002.6 ms
64 bytes from 192.168.0.2: icmp_seq=30 ttl=128 time=9003.1 ms
64 bytes from 192.168.0.2: icmp_seq=31 ttl=128 time=8003.6 ms
64 bytes from 192.168.0.2: icmp_seq=32 ttl=128 time=7004.1 ms
64 bytes from 192.168.0.2: icmp_seq=33 ttl=128 time=6004.6 ms
64 bytes from 192.168.0.2: icmp_seq=34 ttl=128 time=5005.1 ms
64 bytes from 192.168.0.2: icmp_seq=35 ttl=128 time=4005.5 ms
64 bytes from 192.168.0.2: icmp_seq=36 ttl=128 time=3006.0 ms
64 bytes from 192.168.0.2: icmp_seq=37 ttl=128 time=2006.5 ms
64 bytes from 192.168.0.2: icmp_seq=38 ttl=128 time=1007.0 ms
64 bytes from 192.168.0.2: icmp_seq=39 ttl=128 time=7.5 ms
64 bytes from 192.168.0.2: icmp_seq=40 ttl=128 time=0.8 ms
64 bytes from 192.168.0.2: icmp_seq=41 ttl=128 time=0.8 ms

-- 

=====================================================================
BOREK LUPOMESKY                Usti nad Labem, Czech Republic, Europe
WWW: http://www.ujep.cz/~lupomesk/                PGP keyid: B6A06AEB
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