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TOPIC: Blocking dhcp packets in cisco3560 layer3 switch

Blocking dhcp packets in cisco3560 layer3 switch 10 years 5 days ago #17063

Hi,

We have two offices joined with a fiber leased line of 100Mbps.

We have installed 2 layer 3 switches at both the ends to enable routing between the different networks at both the ends.

What commands are to be issues in the cisco3560 layer3 switch to disable the dhcp packets crossover the networks.

Regards,
Naveen.
Thanks & Regards,
Naveen Kollipara.
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Re: Blocking dhcp packets in cisco3560 layer3 switch 10 years 5 days ago #17081

  • havohej
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ok.
dhcp is broadcast traffic, so if you are using layer 3 devices to route between 2 networks, dhcp requests wont be routed unless you use the ip helper address feature.
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Re: Blocking dhcp packets in cisco3560 layer3 switch 10 years 4 days ago #17087

  • Smurf
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Hi,

I have read somewhere that sometimes even with a layer3 switch, the broadcast traffic can still flow (when its not supposed to).

If this is happening, you could try an access list to block the DHCP (BOOTP) traffic ?

I must admit that i am not an expert in this area yet, its just my thoughts on this one.
Wayne Murphy
Firewall.cx Team Member
www.firewall.cx

Now working for a Security Company called Sec-1 Ltd in the UK, for any
Penetration Testing work visit www.sec-1.com or PM me for details.
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