11-11-2007 12:41 AM - edited 03-03-2019 07:30 PM
I am using a cable modem connected to fa0/1 using DHCP on a 2621. I read that first ping is lost due to an ARP lookup. It seems to do a lookup on every address, including public IPs. It is causing every web page request to be delayed.
Config:
version 12.3
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Router2621
!
boot-start-marker
boot-end-marker
!
enable password 7
!
no aaa new-model
ip subnet-zero
!
!
ip dhcp excluded-address 192.168.1.1 192.168.1.99
!
ip dhcp pool 1
import all
network 192.168.1.0 255.255.255.0
default-router 192.168.1.1
!
ip audit po max-events 100
!
!
username Pat password 7
!
!
interface FastEthernet0/0
description Local Network
bandwidth 1200
ip address 192.168.1.1 255.255.255.0
ip nat inside
duplex auto
speed 100
!
interface FastEthernet0/1
description connected to Internet
ip address dhcp
ip nat outside
duplex auto
speed auto
!
ip nat log translations syslog
ip nat inside source list 7 interface FastEthernet0/1 overload
ip http server
no ip http secure-server
ip classless
ip route 0.0.0.0 0.0.0.0 FastEthernet0/1
!
access-list 7 permit 192.168.1.0 0.0.0.255
access-list 100 permit udp any any eq bootpc
!
snmp-server community private RW
snmp-server enable traps tty
!
!
!
!
!
line con 0
exec-timeout 0 0
password 7
login
line aux 0
line vty 0 4
password 7
login
!
end
Solved! Go to Solution.
11-11-2007 01:58 AM
Hi
It's your default-route that is doing it
ip route 0.0.0.0 0.0.0.0 FastEthernet0/1
If your default-route was changed to be
ip route 0.0.0.0 0.0.0.0 "next-hop IP"
then your router would not need to arp for all destinations just the next-hop IP address. But because you have told it the default-route is out of the fa0/1 interface your router will arp out for all destinations.
Do you know what the next hop should be ?. If so change your default-route entry as in example above.
HTH
Jon
11-11-2007 02:14 PM
Hi,
you should replace "FastEthernet0/1" or gateway address in 0.0.0.0 default route with "dhcp". If "command error", then need to upgrade IOS.
In recent code, you don't need to configure the default route at all.
In any case, you also don't need "default-router" that is only for when routing is disabled.
Moreover you don't even need:
ip dhcp excluded-address 192.168.1.1 192.168.1.99
as the roueter will never assign his own address via dhcp.
Hope this helps, please rate post if it does!
11-11-2007 01:58 AM
Hi
It's your default-route that is doing it
ip route 0.0.0.0 0.0.0.0 FastEthernet0/1
If your default-route was changed to be
ip route 0.0.0.0 0.0.0.0 "next-hop IP"
then your router would not need to arp for all destinations just the next-hop IP address. But because you have told it the default-route is out of the fa0/1 interface your router will arp out for all destinations.
Do you know what the next hop should be ?. If so change your default-route entry as in example above.
HTH
Jon
11-11-2007 11:47 AM
I did the command, show dhcp lease
I used the temp default gateway that was in the lease. Works great thanks. Is there a way to have it dynamic? I'm not sure how offen ISP would change that but just curious.
11-11-2007 12:00 PM
Glad it helped.
Default-gateway should not change as long as ISP is leasing out of the same subnet range but it is worth talking to them to find out.
Jon
11-11-2007 02:14 PM
Hi,
you should replace "FastEthernet0/1" or gateway address in 0.0.0.0 default route with "dhcp". If "command error", then need to upgrade IOS.
In recent code, you don't need to configure the default route at all.
In any case, you also don't need "default-router" that is only for when routing is disabled.
Moreover you don't even need:
ip dhcp excluded-address 192.168.1.1 192.168.1.99
as the roueter will never assign his own address via dhcp.
Hope this helps, please rate post if it does!
11-11-2007 02:33 PM
1-99 are static set devices and computers. default router was left over trying routing to fix this. I thought I had 12.2 and it didn't have dhcp as an option. It worked in 12.3 which i tried previously tried before. Thank you ip route 0.0.0.0 0.0.0.0 DHCP is working like a champ.
11-11-2007 02:58 PM
woops I didn't looked the excluded address correctly. that included router address and is all good as well.
Glad to know it helped, please remember to rate posts using the scrollbox below!
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