cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
2119
Views
14
Helpful
22
Replies

IP CEF

xbaha12345
Level 1
Level 1

hello

I am trying to debug why my load balancing is not giving me a 100% of the bandwidth, i tried few commands, if some one please explain what they mean and if there is something wrong in their output:

Router#sh cef not-cef

CEF Packets passed on to next switching layer

Slot No_adj No_encap Unsupp'ted Redirect Receive Options Access Frag

RP 1231 0 3687843 13 290906 0 0 0

Router#sh cef drop

CEF Drop Statistics

Slot Encap_fail Unresolved Unsupported No_route No_adj ChkSum_Err

RP 7308 0 0 6 0 0

#sh ip cef receive

Apr 21 00:57:54.663: CEF-Receive: Packet for 65.55.251.108 -- unsupported featur

e

Apr 21 00:57:54.663: CEF-Receive: Not supported for 208.98.1.46 thru Dialer5 - r

eceive

Apr 21 00:57:54.663: CEF-Receive: Packet for 208.98.1.46 -- unsupported feature

Apr 21 00:57:54.663: CEF-Receive: Not supported for 208.98.1.46 thru Dialer5 - r

eceive

Apr 21 00:57:54.663: CEF-Receive: Packet for 208.98.1.46 -- unsupported feature

Apr 21 00:57:54.663: CEF-Receive: Not supported for 209.73.166.140 thru Dialer2

- receive

22 Replies 22

mohammedmahmoud
Level 11
Level 11

Hi there,

For CEF the Unsupported feature indicates that for the packet received the adjacency route information was dropped due to unsupported features.

By default, Cisco IOS software switches packets using the next fastest switching path (such as optimum, fast, or process switching) when CEF does not support a feature or encapsulation, and i think thats why your load balancing has problems.

For example since Cisco IOS Software Releases 11.2, CEF didn't support these features (I am trying to find out an updated list for you):

* Policy routing

* Network Address Translation (NAT)

* Access lists on the GSR

* Multipoint PPP

* SMDS

* Token Ring

* ATM dixie

* Inter-Switch Link (ISL)

http://www.cisco.com/en/US/products/sw/iosswrel/ps1824/products_feature_guide09186a0080087adc.html

HTH,

Mohammed Mahmoud.

Thanks so much mohammed, i finally got a reply for this...

my version is 12.4, i am using 3845 router.

do you have any idea how to overcome this problem? what makes a packet supported feature and another not supported?

i need a solution if you have any idea please let me know.

thanks.

Hi Baha,

Kindly post your configuration in order to think it out.

BR,

Mohammed Mahmoud.

Hello Mohammed, thanks for your concern, here is the cfg:

version 12.4

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

boot-start-marker

boot-end-marker

!

enable secret xxx

!

aaa new-model

!

!

aaa authentication login default local

!

aaa session-id common

!

resource policy

!

ip subnet-zero

ip cef

ip cef load-sharing algorithm original

!

ip domain name xx.xx.xx.xx

ip name-server xx.xx.xx.xx

vpdn enable

!

!

username xxxx password 0 xxxx

!

!

interface GigabitEthernet0/0

description $ETH-LAN$$ETH-SW-LAUNCH$$INTF-INFO-GE 0/0$

ip address 10.10.10.1 255.255.255.0 secondary

ip address xxx.xx.xx.xx 255.255.255.248

ip nat inside

ip tcp adjust-mss 1452

load-interval 30

duplex auto

speed auto

media-type rj45

negotiation auto

!

interface GigabitEthernet0/1

ip address 192.168.0.1 255.255.0.0

ip nat inside

ip tcp adjust-mss 1452

duplex auto

speed auto

media-type rj45

negotiation auto

!

interface ATM0/1/0

bandwidth 1088

no ip address

no atm ilmi-keepalive

dsl operating-mode auto

hold-queue 224 in

pvc 0/35

encapsulation aal5mux ppp dialer

dialer pool-member 1

!

!

interface ATM0/2/0

bandwidth 1088

no ip address

no atm ilmi-keepalive

dsl operating-mode auto

hold-queue 224 in

pvc DSL 0/35

encapsulation aal5mux ppp dialer

dialer pool-member 2

!

!

interface ATM0/3/0

bandwidth 1088

no ip address

logging event atm pvc state

no atm ilmi-keepalive

dsl operating-mode auto

hold-queue 224 in

pvc 0/35

encapsulation aal5mux ppp dialer

dialer pool-member 3

!

interface ATM3/0/0

bandwidth 1088

no ip address

no atm ilmi-keepalive

dsl operating-mode auto

hold-queue 224 in

pvc 0/35

encapsulation aal5mux ppp dialer

dialer pool-member 4

!

interface Dialer1

mtu 1492

bandwidth 1024

ip address negotiated

ip nat outside

encapsulation ppp

dialer pool 1

dialer-group 1

no cdp enable

ppp authentication pap callin

ppp chap refuse

ppp pap sent-username xxx password 0 xxx

!

interface Dialer2

mtu 1492

bandwidth 1024

ip address negotiated

ip nat outside

encapsulation ppp

dialer pool 2

no cdp enable

ppp authentication pap callin

ppp chap refuse

ppp pap sent-username xxx password 0 xxxx

!

interface Dialer3

mtu 1492

bandwidth 1024

ip address negotiated

ip nat outside

encapsulation ppp

dialer pool 3

no cdp enable

ppp authentication pap callin

ppp chap refuse

ppp pap sent-username xxx password 0 xxx

!

interface Dialer4

mtu 1492

bandwidth 1024

ip address negotiated

ip nat outside

encapsulation ppp

dialer pool 4

dialer-group 4

ppp authentication pap callin

ppp chap refuse

ppp pap sent-username xxx password 0 xxx

!

ip classless

ip route 0.0.0.0 0.0.0.0 Dialer1

ip route 0.0.0.0 0.0.0.0 Dialer2

ip route 0.0.0.0 0.0.0.0 Dialer3

ip route 0.0.0.0 0.0.0.0 Dialer4

!

ip nat inside source route-map Connection_1 interface Dialer1 overload

ip nat inside source route-map Connection_2 interface Dialer2 overload

ip nat inside source route-map Connection_3 interface Dialer3 overload

ip nat inside source route-map Connection_4 interface Dialer4 overload

!

no logging trap

access-list 1 permit 192.168.0.0 0.0.255.255

access-list 1 permit 10.10.10.0 0.0.0.255

access-list 10 permit 10.10.10.9

access-list 101 permit ip 10.10.10.0 0.0.0.255 any

access-list 101 permit ip 192.168.0.0 0.0.255.255 any

dialer-list 1 protocol ip permit

snmp-server community xxx RO

!

route-map Connection_1 permit 10

match ip address 1

match interface Dialer1

!

route-map Connection_2 permit 10

match ip address 1

match interface Dialer2

!

route-map Connection_3 permit 10

match ip address 1

match interface Dialer3

!

route-map Connection_4 permit 10

match ip address 1

match interface Dialer4

!

Hi Baha,

why did you configure the "ip cef load-sharing algorithm original "

The following load-balancing algorithms are provided for use with CEF traffic. You select a load balancing algorithm with the ip cef load-sharing algorithm command.

?Original algorithm?The original CEF load-balancing algorithm produced distortions in load sharing across multiple routers because the same algorithm was used on every router. Depending on your network environment, you should select either the universal algorithm (default) or the tunnel algorithm.

?Universal algorithm?The universal load-balancing algorithm allows each router on the network to make a different load sharing decision for each source-destination address pair, which resolves load-sharing imbalances. The router is set to perform universal load sharing by default.

?Tunnel algorithm?The tunnel algorithm is designed to balance the per-packet load when only a few source and destination pairs are involved.

http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a0080430ac3.html

BR,

Mohammed Mahmoud.

Hello Mohammed,

i tried this ip cef load-sharing algorithm original, after many trials, now i removed this line, i still recieve many 'Unsupported feature' when i debug ip cef receive.

is it my router limitations?

does the rest of my config looks fine?

thanks for you help.

Hi Baha,

There is nothing wrong with your configuration.

May be the combination of your configuration (NAT, load-sharing and route-maps) have produced the unsupported feature. (Note that the unsupported feature packets are not dropped, they are normally fast switched which should not affect your BW utilization).

How are you testing your BW utilization ?

BR,

Mohammed Mahmoud.

hi

my BW utilization is about 25% - 30% for each line.

even when i try to download something when the 4 lines at 25-30%, i dont get much bandwidth (2-3kbyte/s) and the download stops usually.

if i immeadiatly remove the line from the Cisco Router, and plugged it to a normal ADSL modem, i get 100% of the bandwidth!

anyway to trace what's really happening?

is there a diffrent or better way for load sharing?

thanks.

Hi Baha,

I am really trying to help you out here, you are load-sharing per-destination which is fine with no problems, i am suspecting the MSS and MTU issue as it always affect the TCP performance.

interface GigabitEthernet0/0

ip tcp adjust-mss 1452

interface Dialer2

mtu 1492

BR,

Mohammed Mahmoud.

hello mohammed,

i put this:

ip tcp adjust-mss 1452

because people couldnt login to yahoo or MSN

any suggestions to change the value?

also any suggestions to change the MTU?

thanks!

Dear Baha,

The Dialer CEF feature is not supported when a static route is pointing to the Dialer without specifying a next hop IP address. When using the Cisco IOS Release 12.3(11)T and higher, the ppp ipcp default route command may be used in Dialer interface configuration mode to work around this restriction.

CEF was not supported over dialer interface (older IOS's)

Use the below URL for more information

http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a008049b0ea.html#wp1029310

Dialer10 is up (if_number 8)

Corresponding hwidb fast_if_number 8

Corresponding hwidb firstsw->if_number 8

Internet Protocol processing disabled

Interface is marked as point to point interface

Packets switched to this interface are dropped to the next slow path: Dialer

Hardware idb is Dialer10

Fast switching type 15, interface type 85

(the above line said the packets recieved over dialer interface will be switched to next level switching)

Please rate helpful posts.

Best Regards,

Mounir Mohamed

Dear Baha,

Please try the above solution and feedback us.

BR,

Mohammed Mahmoud.

hello mohammed,

i have added ppp ipcp route default in each dialer int..

nothing has changed!

#debug ip cef rec

.Apr 23 21:24:12.412: IP-CEF: Receive packet for 88.84.97.8 (process switch)

.Apr 23 21:24:12.412: CEF-Receive: Not supported for 216.34.130.245 thru Dialer3

- receive

.Apr 23 21:24:12.412: CEF-Receive: Packet for 216.34.130.245 -- unsupported feat

ure

.Apr 23 21:24:12.428: CEF-Receive: Not supported for 84.48.216.192 thru Dialer1

- receive

.Apr 23 21:24:12.428: CEF-Receive: Packet for 84.48.216.192 -- unsupported featu

re

.Apr 23 21:24:12.428: CEF-Receive: Not supported for 207.46.106.70 thru Dialer6

- receive

.Apr 23 21:24

i dont really care for this messgae as much as i am not getting my 100% of the bandwidth, so any suggestion what to change the values of MTU & MSS?

thanks again and really appreciate your help.

Dear Baha,

Did you route the default/static route to the next-hop, the PDF said the problem usually happen when the default/static routes pointing to the dialer interface

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community:

Innovations in Cisco Full Stack Observability - A new webinar from Cisco