09-27-2018 11:41 AM - edited 03-08-2019 04:15 PM
Hello,
Below is the general question, I can provide any sh command output.
I have a router with several VLAN’s configured, and need to have a trunk from the router to
a c4948 switch. With global and interface CEF enabled on the router layer 2 trunk GigE interface it is not
using CEF but is process switching packets, and that is bringing throughput to a crawl. If I change
the router and switch interfaces to layer 3 and assign IP’s to both will the link be able to forward
packets from all VLAN’s due to the FIB? How can I enable CEF on this link?
Thank you
09-27-2018 11:47 AM
Hello,
CEF is a layer 3 switching technology and has nothing to do with trunks. What are you trying to configure, a router on a stick ?
09-27-2018 02:01 PM
I have a router running several vlan's with a trunking GigE interface that connects to a c4948 trunking GigE interface. The inbound queue of the router interface is dropping packets at a massive rate because it is process switching due to not CEF processing. What would be the best configuration to increase throughput?
Both trunk ports have the following configuration
Router
Name: Gi1/0
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: Disabled
Access Mode VLAN: 0 ((Inactive))
Trunking Native Mode VLAN: 1 (default)
Trunking VLANs Enabled: ALL
Trunking VLANs Active: 1-2,5-8,10
Protected: false
Priority for untagged frames: 0
Override vlan tag priority: FALSE
Voice VLAN: none
Appliance trust: none
Switch
Name: Gi1/48
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: Off
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: 1,2,5-8,10
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Thank you
09-27-2018 02:07 PM
Hello,
post the output of 'show interfaces x' for both interfaces...
09-27-2018 02:17 PM
Sure,
Router port
#sh interfaces gigabitEthernet 1/0
GigabitEthernet1/0 is up, line protocol is up
Hardware is Gigabit Ethernet, address is c471.fe4a.9b4b (bia c471.fe4a.9b4b)
Description: Trunk to 4948_left
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
output flow-control is off, input flow-control is off
0 pause input, 0 pause output
Full-duplex, 1000Mb/s
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:01, output never, output hang never
Last clearing of "show interface" counters 2w6d
Input queue: 0/100/42251936/0 (size/max/drops/flushes); Total output drops: 13597
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 189000 bits/sec, 106 packets/sec
5 minute output rate 523000 bits/sec, 108 packets/sec
1145572748 packets input, 1645937597 bytes, 0 no buffer
Received 883100 broadcasts (0 multicasts)
0 runts, 0 giants, 0 throttles
4071 input errors, 1 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
0 input packets with dribble condition detected
1870048228 packets output, 1250264857 bytes, 0 underruns
1 output errors, 0 collisions, 0 interface resets
2767 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out
Switch port
#sh interfaces gigabitEthernet 1/48
GigabitEthernet1/48 is up, line protocol is up (connected)
Hardware is Gigabit Ethernet Port, address is 001d.a26e.c42f (bia 001d.a26e.c42f)
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/s, link type is auto, media type is 10/100/1000-TX
Media-type configured as RJ45 connector
input flow-control is off, output flow-control is off
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:01, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 462000 bits/sec, 105 packets/sec
5 minute output rate 184000 bits/sec, 110 packets/sec
17731231901 packets input, 20773959580119 bytes, 0 no buffer
Received 65887959 broadcasts (56821798 multicast)
0 runts, 0 giants, 0 throttles
1 input errors, 1 CRC, 0 frame, 0 overrun, 0 ignored
0 input packets with dribble condition detected
13275562125 packets output, 6161807353824 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
Thank you
09-27-2018 02:29 PM
Hello,
on your router, change the hold queue to 2000 (which equals the hold queue on the other side):
Router#conf t
Router(config)#int gigabitEthernet 1/0
Router(config-if)#hold-queue 2000 in
Router(config-if)#end
09-27-2018 03:31 PM
I increased the router interface inbound queue to 2000 and no change in inbound queue packet drops.
Thank you
-John
09-28-2018 01:04 AM
Hello,
what is the output of 'show interfaces GigabitEthernet0/1 switching' (this is a hidden command so you need to type the entire string) ?
Have you enabled fast switching on the router and/or the interface ?
interface GigabitEthernet0/1
ip route-cache
What platform is this anyway (e.g. 3925, 4331) ?
09-28-2018 09:31 AM
Hi,
This is a 3845 router, and the interface is a layer 2 trunk, can't enable ip route-cache
Sorry about the formatting of the show command below.
#sh interfaces gigabitEthernet 1/0 switching
GigabitEthernet1/0 Trunk
Throttle count 0
Drops RP 49493936 SP 0
SPD Flushes Fast 0 SSE 0
SPD Aggress Fast 0
SPD Priority Inputs 0 Drops 0
Protocol DEC MOP
Switching path Pkts In Chars In Pkts Out Chars Out
Process 0 0 3420 263340
Cache misses 0 - - -
Fast 0 0 0 0
Auton/SSE 0 0 0 0
Protocol Spanning Tree
Switching path Pkts In Chars In Pkts Out Chars Out
Process 509 22224 8212372 521485580
Cache misses 0 - - -
Fast 0 0 0 0
Auton/SSE 0 0 0 0
Protocol CDP
Switching path Pkts In Chars In Pkts Out Chars Out
Process 34128 14353782 34252 13255524
Cache misses 0 - - -
Fast 0 0 0 0
Auton/SSE 0 0 0 0
Protocol VTP
Switching path Pkts In Chars In Pkts Out Chars Out
Process 0 0 3492 360084
Cache misses 0 - - -
Fast 0 0 0 0
Auton/SSE 0 0 0 0
Protocol Other
Switching path Pkts In Chars In Pkts Out Chars Out
Process 2812 168720 0 0
Cache misses 0 - - -
Fast 0 0 0 0
Auton/SSE 0 0 0 0
09-28-2018 03:38 PM - edited 09-28-2018 04:53 PM
09-28-2018 04:54 PM
The VLAN’s are configured with default route on the router, but not as subinterfaces on the GigE
trunk interface. If I perform the following steps I should avoid process switching and be able to use CEF on the GigE interface correct?
Then CEF and not process switching should be used correct?
Thank you
09-29-2018 01:37 AM
Hello,
your traffic volume is low, there should be no drops at all. Are these RJ-45, GBIC, or SFP connections ? Try to set the media type on the interface of the 3845, also increase the output hold queue and the queuing strategy:
interface GigabitEthernet1/0
fair-queue
hold-queue 2000 out
media-type gbic/rj45/sfp
09-29-2018 04:36 AM - edited 09-29-2018 04:41 AM
Hello
@rugman66 wrote:
Hello,
How can I enable CEF on this link?
On the physical or SVI interface:
int x/x
ip route-cache cef
end
show ip int x/x | in IP
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