slow speed with cisco 3620

kozlojak · June 2007

I have a 4-5mb connection with my linksys router, however when I set my cisco 3620 up with NAT I can only get 1.5-1.7mb any ideas off hand?

!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Internet
!
boot-start-marker
boot-end-marker
!
enable secret 5 $1$FDNE$g8RmVxZLygVR6I08l4N031
!
no aaa new-model
ip subnet-zero
!
!
ip cef
ip dhcp excluded-address 10.10.1.1 10.10.1.100
!
ip dhcp pool INTERNAL
network 10.10.1.0 255.255.255.0
default-router 10.10.1.1
dns-server 64.71.255.198
!
!
partition flash 2 16 8
!
!
!
!
interface Ethernet0/0
ip address dhcp
ip nat outside
logging event subif-link-status
full-duplex
!
interface Serial0/0
no ip address
logging event subif-link-status
shutdown
no fair-queue
!
interface TokenRing0/0
no ip address
logging event subif-link-status
shutdown
ring-speed 16
!
interface Ethernet1/0
ip address 10.10.1.1 255.255.255.0
ip nat inside
logging event subif-link-status
full-duplex
!
interface Ethernet1/1
no ip address
logging event subif-link-status
shutdown
half-duplex
!
ip nat inside source list 1 interface Ethernet0/0 overload
no ip http server
ip classless
!
!
access-list 1 permit 10.10.1.0 0.0.0.255
banner motd
****************************************************************
*
* WARNING: System is RESTRICTED to authorized personnel ONLY!
* Unauthorized use of this system will be logged and
* prosecuted to the fullest extent of the law.
*
* If you are NOT authorized to use this system, LOG OFF NOW!
*
****************************************************************
!
line con 0
line aux 0
line vty 0
password
login
line vty 1 4
login
!
!
end

dtlokee · June 2007

Half duplex ethernet perhaps. If you're talking about the transfer rate in Megabytes per second:

10,000,000 bits per second / 8 = 1,250,000 Bytes/second or roughly 1.25 Megabytes per second.

Or it could be an interface problem, perhaps you could look at the output of show interface and look for a high error rate. I f you're connected via a crossover to the modem or csu/dsu you may want to try setting full duplex.

Other than that it looks okay.

malcybood · June 2007

kozlojak wrote:

I have a 4-5mb connection with my linksys router, however when I set my cisco 3620 up with NAT I can only get 1.5-1.7mb any ideas off hand?

!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Internet
!
boot-start-marker
boot-end-marker
!
enable secret 5 $1$FDNE$g8RmVxZLygVR6I08l4N031
!
no aaa new-model
ip subnet-zero
!
!
ip cef
ip dhcp excluded-address 10.10.1.1 10.10.1.100
!
ip dhcp pool INTERNAL
network 10.10.1.0 255.255.255.0
default-router 10.10.1.1
dns-server 64.71.255.198
!
!
partition flash 2 16 8
!
!
!
!
interface Ethernet0/0
ip address dhcp
ip nat outside
logging event subif-link-status
full-duplex
!
interface Serial0/0
no ip address
logging event subif-link-status
shutdown
no fair-queue
!
interface TokenRing0/0
no ip address
logging event subif-link-status
shutdown
ring-speed 16
!
interface Ethernet1/0
ip address 10.10.1.1 255.255.255.0
ip nat inside
logging event subif-link-status
full-duplex
!
interface Ethernet1/1
no ip address
logging event subif-link-status
shutdown
half-duplex
!
ip nat inside source list 1 interface Ethernet0/0 overload
no ip http server
ip classless
!
!
access-list 1 permit 10.10.1.0 0.0.0.255
banner motd
****************************************************************
*
* WARNING: System is RESTRICTED to authorized personnel ONLY!
* Unauthorized use of this system will be logged and
* prosecuted to the fullest extent of the law.
*
* If you are NOT authorized to use this system, LOG OFF NOW!
*
****************************************************************
!
line con 0
line aux 0
line vty 0
password
login
line vty 1 4
login
!
!
end

dtlokee beat me to it but half duplex on int eth 1/1 jumps right out at me from the config output.

malcybood · June 2007

Just to add, I would also try setting the ethernet port 1/0???? that connects to the Linksys to auto duplex unless you know 100% that your linksys is set to full duplex.

If there is a duplex mismatch between the linksys and 3620 or the 3620 port and a host it can cause slow connection speeds.

the command to set it to auto is just duplex auto from the interface config mode

kozlojak · June 2007

e 1/0 is full duplex as it should be connected to a cisco switch. e0/0 will only work in half if i set to full it will not communicate to the internet at all it is connected to a webstar cable modem. if i put it to full duplex i can ping but can not open any web pages it just times out.

when I debug I am getting alote of "IP ARP" traffic is this a problem?

is it possable the cable modem is to blame even thow it will work fine with the linksys?

dtlokee · June 2007

Hmmm I missed it before, you don't have a default route in the config you've posted. If you're getting lots of arp requests could be the souce of the problem.

kozlojak · June 2007

the default route is there the router creates it on its own after it gets an ip from the dhcp. i have also set a default rout manually but still have the same problem, is there anyway around the arp problem?

cambei · June 2007

I know you said it is cable, but on ADSL in the UK, dropping the MTU to about 1458 or even 1432 can improve speeds dramatically as the packets are less likely to need to be fragmented.

slow speed with cisco 3620

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