Cisco Support Community
Community Member

all upd ports r open

all the ports are open on one of my internet gateway router. this is a big security vulnerability. y all these ports r open? may be DDOS attack or...

plz help me.

Cisco Employee

Re: all upd ports r open

I'll guarantee you that all the UDP ports are NOT open on your router. UDP port scanning is unreliable to say the least, since you can't really connect to a UDP port. Some UDP port scanners rely on receiving ICMP Unreachables from the scanned device, and if it doesn't return them then it assumes they're open. This is wrong.

Try a couple of other port scanners and you'll find you get very different results.

For router security follow this:

Community Member

Re: all upd ports r open

thank you very much for ur reply.

i used nmap tool from a linux machine. when i scan another router i found only two ports open. but on this gateway router almost all udp ports were open.

can u suggest me any other port scanner?

Community Member

Re: all upd ports r open

thanks. my problem has solved. that was ICMP Unreachable problem only. i enabled ip unreachable and then scanned. it showed only four ports open.


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