move cable from eth1 to eth0, but cannot ping eth0
hi everyone,
we designed embedded board, running basic linux, no fancy stuff (e.g. network manager). it has 2 ethernet ports: eth0, eth1 1. plugin cable to eth1, restart board. it comes back, eth1 is alive, i can ping it. 2. move the cable from eth1 to eth0, run "udhcpc --reties 4 -n -q -i eth0" ifconfig shows eth0 now has a valid ip addr, also it's UP. 3. but i cannot ping eth0 i'm not familiar with network stuff, the 2 device drivers for the 2 ports are working (in the sense i just plug in 1 cable each time). does that mean the network stack is wrong ? can someone walk through me with these ? |
I guess your lan may have some issue maybe arp. I don't like to use ping myself. Is this between a computer to this board? Does it work on 0 from boot with cable attached?
Use ifconfig to set static ip in your lan subnet. Be sure to flush arp or wait a while until it clears out. |
Jefro,
you are making the right suggestion, i got it but don't know how to fix it. 1. say initially i have ethernet cable in eth0 for this embedded board, after reboot, arp -n says ? (10.50.182.160) at bc:30:5b:df:b9:25 [ether] on eth0 2. move cable from eth0 to eth1, # udhcpc --retries 4 -n -q -i eth1 eth1 is up 3. # arp -n ? (10.50.182.160) at <incomplete> on eth0 ping doesn't work for eth1 4. # arp -d 10.50.182.160 -i eth0 it doesn't return error, but the arp entry is still there 5. if i do ifconfig eth0 down, now arp table is clean if i try all these in my desktop linux, arp table gets updated as soon as i move the cable. so i'm so lost now, 1. why "arp -d" doesn't work ? 2. if i don't want to do "ifconfig eth0 down", it might involved too much is there an easy way ? thanks for your help ! Quote:
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I may not have said that well. I meant that arp on the other segment.
Describe lan segment. |
i believe this is our linux kernel/driver problem, arp is totally messed up.
just 1 board with 2 NICs, both NICs connects to the same router. after i disconnect eth0 cable, if i play with with "arp -d", "ifconfig eth0 up/down" with different combinations, i could still ping eth0 even without the cable. but any thoughts are welcome. Quote:
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