[c-nsp] "Packets dropped to the next slow path"
Vincent De Keyzer
vincent at dekeyzer.net
Mon Nov 21 09:50:54 EST 2005
There is a show interface at the bottom of the mail; but I don't think it's
a QoS problem, because problem started when this customer was moved from one
router to another. For me it's more CEF-related - packets not being
CEF-switched, but I'm not sure.
Vincent
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> bounces at puck.nether.net] On Behalf Of Ray Burkholder
> Sent: lundi 21 novembre 2005 15:42
> To: Vincent De Keyzer
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] "Packets dropped to the next slow path"
>
> How much traffic is going through the interface? Can you do a show
> interface?
> Voice is Delay and drop sensitive. There are a number of commands for
> properly
> grooming voice traffic if this is a QoS issue.
>
> Quoting Vincent De Keyzer <vincent at dekeyzer.net>:
>
> > Hello,
> >
> >
> >
> > I have a customer complaining of micro-cuts during his (VoIP) phone
> > conversations.
> >
> >
> >
> > Here is the config of his interface:
> >
> >
> >
> > interface Serial6/0:0
> >
> > mac-address 0014.a862.b71b
> >
> > ip address 10.11.130.33 255.255.255.224 secondary
> >
> > ip address 10.11.133.1 255.255.255.224 secondary
> >
> > ip address x.y.z.5 255.255.255.252
> >
> > ip verify unicast reverse-path
> >
> > no ip redirects
> >
> > no ip unreachables
> >
> > no ip proxy-arp
> >
> > encapsulation ppp
> >
> > load-interval 30
> >
> > no fair-queue
> >
> > no cdp enable
> >
> > ppp bridge ip
> >
> > end
> >
> >
> >
> > We already had similar problems a few months ago, and it was due to an
> > interface not being CEF-enabled - every second, the BGP scanner process
> > would use a lot of CPU, and delay packets being processed centrally.
> >
> >
> >
> > Having that in mind, I looked at "sh cef interface":
> >
> >
> >
> > BRULEOro72#sh cef interface serial 6/0:0
> >
> > Serial6/0:0 is up (if_number 59)
> >
> > Corresponding hwidb fast_if_number 59
> >
> > Corresponding hwidb firstsw->if_number 59
> >
> > Internet address is x.y.z.5/30
> >
> > Secondary address 10.11.130.33/27
> >
> > Secondary address 10.11.133.1/27
> >
> > ICMP redirects are never sent
> >
> > Per packet load-sharing is disabled
> >
> > IP unicast RPF check is enabled
> >
> > Input features: Verify Unicast Reverse-Path
> >
> > Inbound access list is not set
> >
> > Outbound access list is not set
> >
> > IP policy routing is disabled
> >
> > BGP based policy accounting on input is disabled
> >
> > BGP based policy accounting on output is disabled
> >
> > Interface is marked as point to point interface
> >
> > IPv4 packets switched to this interface are dropped to the next slow
> path:
> > PPP - not open
> >
> > Hardware idb is Serial6/0:0
> >
> > Fast switching type 7, interface type 13
> >
> > IP CEF switching enabled
> >
> > IP CEF switching turbo vector
> >
> > IP CEF turbo switching turbo vector
> >
> > IP prefix lookup IPv4 mtrie 8-8-8-8 optimized
> >
> > Input fast flags 0x4000, Output fast flags 0x0
> >
> > ifindex 11(11)
> >
> > Slot 6 Slot unit 0 VC 0
> >
> > Transmit limit accumulator 0x0 (0x0)
> >
> > IP MTU 1500
> >
> >
> >
> > It's the "IPv4 packets switched to this interface are dropped to the
> next
> > slow path: PPP - not open" that worries me: what does this mean ? Are
> the
> > packets CEF-switched, or not ?
> >
> >
> >
> > PPP seems to be up:
> >
> >
> >
> > BRULEOro72#sh interfaces s6/0:0
> >
> > Serial6/0:0 is up, line protocol is up
> >
> > Hardware is Multichannel E1
> >
> > Internet address is x.y.z.5/30
> >
> > MTU 1500 bytes, BW 1984 Kbit, DLY 20000 usec,
> >
> > reliability 255/255, txload 20/255, rxload 177/255
> >
> > Encapsulation PPP, crc 16, Data non-inverted
> >
> > Keepalive set (10 sec)
> >
> > ARP type: ARPA, ARP Timeout 04:00:00
> >
> > LCP Open
> >
> > Open: BRIDGECP
> >
> > Last input 3d15h, output 00:00:00, output hang never
> >
> > Last clearing of "show interface" counters 3d18h
> >
> > Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
> 2565
> >
> > Queueing strategy: fifo
> >
> > Output queue: 0/40 (size/max)
> >
> > 30 second input rate 1381000 bits/sec, 172 packets/sec
> >
> > 30 second output rate 157000 bits/sec, 132 packets/sec
> >
> > 3059499 packets input, 1503754010 bytes, 0 no buffer
> >
> > Received 0 broadcasts (0 IP multicast)
> >
> > 0 runts, 0 giants, 0 throttles
> >
> > 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
> >
> > 2965137 packets output, 2160279388 bytes, 0 underruns
> >
> > 0 output errors, 0 collisions, 0 interface resets
> >
> > 0 output buffer failures, 0 output buffers swapped out
> >
> > 0 carrier transitions
> >
> > no alarm present
> >
> > Timeslot(s) Used:1-31, subrate: 64Kb/s, transmit delay is 0 flags
> >
> >
> >
> > This is 12.2(25)S4 on a 7206VXR.
> >
> >
> >
> > Vincent
> >
> > _______________________________________________
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> >
>
>
> --
> Ray Burkholder
> http://www.oneunified.net
> ray at oneunified.net
> 441 505 7293
>
> -------------------------------------------------
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>
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