From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Mon Dec 15 2003 - 17:52:22 GMT-3
Alec,
Technically the "ip forward-protocol udp" command does need to be
configured to forward dhcp requests with the "ip helper-address" command.
It's just that "ip forward-protocol udp bootps" is default:
Router(config)#ip forward-protocol udp 67
Router(config)#do sh run | in forward-protocol
Router(config)#no ip forward-protocol udp 67
Router(config)#do sh run | in forward-protocol
no ip forward-protocol udp bootps
If you disable the port, as Chuck suggested, the packet cannot be
forwarded.
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 708-362-1418 (Outside the US and Canada)
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Pun, Alec CL
> Sent: Monday, December 15, 2003 1:56 AM
> To: Jonathan Hays; ccielab@groupstudy.com
> Subject: RE: ip helper-address
>
> thanks guys.
>
> rgds,
> alec
>
> -----Original Message-----
> From: Jonathan Hays [mailto:nomad@gfoyle.org]
> Sent: Monday, December 15, 2003 10:14 AM
> To: ccielab@groupstudy.com
> Subject: RE: ip helper-address
>
>
> you wrote:
> so that means the following pairs of command MUST be used together ?
> thanks.
>
> 1) if default 8 ports are required
> ip helper-address
> ip forward-protocol udp
>
> 2) if additional udp port is required
> ip helper-address
> ip forward-protocol udp <new_port>
>
> rgds,
> alec
>
> = = =
>
> No.
>
> The "ip forward-protocol" command is NOT necessary in case 1). I have
> set up routers with only "ip helper-address" configured many, many
> times. It works. I doubt you will take my word for it, so look at this
> URL.
>
>
> http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/
> fipras_r/1rfipadr.htm#1018608
>
> "The UDP destination port must be for TFTP, Domain Name System (DNS),
> Time, NetBIOS, ND, BOOTP or DHCP packet, or a UDP port specified by the
> ip forward-protocol udp global configuration command."
>
>
> Carefully note the word "or" in the sentence above. If the desired
> port(s) is in the "ip helper-address" list of ports then no "ip
> forward-protocol" command need be configured.
>
> Also, look at the example in the same URL:
>
> "Examples
>
> The following example defines an address that acts as a helper address:
>
> interface ethernet 1
> ip helper-address 121.24.43.2"
>
> The "ip forward-protocol" command is used only if you need to forward a
> port that is not in the standard "helper-address" ports, or disable
> forwarding for one or more of the default "helper-address" ports.
>
> HTH,
>
> Jonathan
>
> _______________________________________________________________________
> Please help support GroupStudy by purchasing your study materials from:
> http://shop.groupstudy.com
>
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
> _______________________________________________________________________
> Please help support GroupStudy by purchasing your study materials from:
> http://shop.groupstudy.com
>
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Sat Jan 03 2004 - 08:25:41 GMT-3