From: Huan Pham (Huan.Pham@peopletelecom.com.au)
Date: Fri Aug 22 2008 - 00:01:07 ART
Hi Wilson
The second one (with dhcp keyword) is a better option. It will tie the
default route with a next-hop IP of the gateway.
Have a close look at the difference btw the two static route when you do
"show ip route static"
R2#sh run | in ip route
ip route 0.0.0.0 0.0.0.0 FastEthernet0/0
R2#sh ip route static
S* 0.0.0.0/0 is directly connected, FastEthernet0/0
R2#sh run | in ip route
ip route 0.0.0.0 0.0.0.0 FastEthernet0/0 dhcp
R2#sh ip route static
S* 0.0.0.0/0 [1/0] via 10.1.1.1, FastEthernet0/0
Having a default route pointing to a multipoint interface (e.g.
fastehternet) without the next hop IP, your router will be overwhelm
with lot of ARP entries (if proxy ARP is enabled on the ISP DHCP
router). Basically, for every Internet destination IP, your router will
need to ARP for MAC address. The DHCP server will respond with an arp
entry for that IP with its own MAC address. Your router will maintain
all ARP entries for every IP on the Internet that your users try to
reach. I do not think you want your routers to have potentially a
million entry ARPcache table!
Regards,
Huan
On Thu, Aug 21, 2008 at 9:11 PM, Wilson Chan
<wilson@wilsonch.gotdns.com>wrote:
> I stumbled upon the "dhcp" option in setting a default route. Is there
> a difference between the two route statements in the example below and
> if there is which is the preferred way and why? Thanks!
>
>
> interface FastEthernet0
> description ***To ISP***
> ip address dhcp
>
> ip route 0.0.0.0 0.0.0.0 FastEthernet0 ip route 0.0.0.0 0.0.0.0
> FastEthernet0 dhcp
>
>
>
> Wilson
>
>
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