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New Member

Problem creating subinterface

Hi

I have a problem on a 6504 running IOS bootdisk:s2t54-advipservicesk9-mz.SPA.151-1.SY.bin.

When I try to create a subinterface the following log entry occours and the subinterface does not work.

*Jul 29 14:58:19.402 CET+1: %EARL-2-LDB_OUT_OF_RESOURCE: Out Of LDB resources. A

llocate 4096 entries failed.

Jul 29 14:58:19.402 CET+1: %EARL-DFC2-2-LDB_OUT_OF_RESOURCE: Out Of LDB resource

s. Allocate 4096 entries failed.

I have 4 other 6504s with almost identical configuration and they have more subinterfaces. But the problem only exists on this one switch.

The physical interface is up and so is the line protocol. And I can see CDP information about the attached switch on that interface.

Here is some configuration:

interface GigabitEthernet2/48
no ip address
!
interface GigabitEthernet2/48.479
description *** MGT ***
encapsulation dot1Q 479
ip address 10.50.226.1 255.255.255.0
no ip redirects
no ip proxy-arp
arp timeout 300
!

GigabitEthernet2/48.479 is up, line protocol is up (connected)
  Hardware is C6k 1000Mb 802.3, address is 0006.f6e9.f880 (bia 0006.f6e9.f880)
  Description: *** MGT ***
  Internet address is 10.50.226.1/24
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation 802.1Q Virtual LAN, Vlan ID  479.
  ARP type: ARPA, ARP Timeout 00:05:00
  L2 Switched: ucast: 0 pkt, 0 bytes - mcast: 0 pkt, 0 bytes
  L3 in Switched: ucast: 0 pkt, 0 bytes - mcast: 0 pkt, 0 bytes
  L3 out Switched: ucast: 390 pkt, 30420 bytes - mcast: 0 pkt, 0 bytes

Have anyone seen this before and can someone explain to me what LDB is in this context?

Thanks

Thomas

Everyone's tags (3)
1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Problem creating subinterface

Hi Thomas,

Logical interfaces are both SVIs and sub-interfaces. And while SVIs does not take much of memory, each sub-interface takes 4k, so their number is limited.

You can check the available memory with command "show plat hard lif l2 memory". It is possible you are really low on it. I think it is up to 30 sub-interfaces on regular sup2T and ~90 on XL version.

Note that LDP resources check is recent code change and earlier would not show such warnings.

Kind Regards,
Ivan Shirshin

**Please grade this post if you find it useful.

Kind Regards, Ivan Shirshin **Please grade this post if you find it useful.
10 REPLIES
VIP Super Bronze

Problem creating subinterface

Hi Thomas,

Do you have same IOS version and feature set on your other 4 6500 switches?

New Member

Re: Problem creating subinterface

Hi
Yes. They are identical.

Sent from Cisco Technical Support iPhone App

Cisco Employee

Problem creating subinterface

Thomas,

According to:

http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCtz70317

LDB appears be a shorthand for Logical interface Descriptor Block, a data structure describing an interface. If the IOS memory allocated for storing LDBs is exhausted, no more SVIs or subinterfaces can be created. Former IOS versions did not report when this problem occured and just silently failed to initialize the hardware. The IOS version you are running has been specifically updated to report such occurences and to keep the affected SVIs and subinterfaces err-disabled.

The question is why this problem occurs on your particular switch. It may truly mean that it is somehow hitting the maximum limit of the allocated memory for given number of logical interfaces (SVIs, subinterfaces, loopbacks, tunnels, etc.). Then again, it may be a bug. I do not know if you can schedule a reload of this box and see whether the problem reappears after reload. In the quoted bug report, there is no workaround specified and they are adamant that the switch is simply exceeding the supported limit of LDBs.

Best regards,

Peter

New Member

Re: Problem creating subinterface

Hi Peter

Thanks for the URL and the explenation.

As far as I can tell from the datasheet for the Sup2T supervisor, it should be able to handle 128k logical interfaces.

http://www.cisco.com/en/US/prod/collateral/modules/ps2797/ps11878/data_sheet_c78-648214_ps708_Products_Data_Sheet.html

There is no more than 200 locigal interfaces on this switch. It's a roughly estimate. But still far far far away from 128k.

I could not find a command like "show lif summary". Is there such a command?

Peter Paluch wrote:

The IOS version you are running has been specifically updated to report such occurences and to keep the affected SVIs and subinterfaces err-disabled.

The subinterfaces are not err-disabled. And if I am understanding the data sheet correctly there should be enough memory for another 127k interfaces.

The switch was reloaded a week ago without results.

Thanks again Peter

Best regards

Thomas

Cisco Employee

Re: Problem creating subinterface

Hi Thomas,

I am afraid this is an issue worth of contacting TAC if possible.

Regarding the LIFs... can you actually have a look into show idb and related commands? IDB stands for Interface Descriptor Block. That is the name I've always known for a structure that describes an interface in IOS. Perhaps its output will move us further.

Best regards,

Peter

Cisco Employee

Problem creating subinterface

Hi Thomas,

Logical interfaces are both SVIs and sub-interfaces. And while SVIs does not take much of memory, each sub-interface takes 4k, so their number is limited.

You can check the available memory with command "show plat hard lif l2 memory". It is possible you are really low on it. I think it is up to 30 sub-interfaces on regular sup2T and ~90 on XL version.

Note that LDP resources check is recent code change and earlier would not show such warnings.

Kind Regards,
Ivan Shirshin

**Please grade this post if you find it useful.

Kind Regards, Ivan Shirshin **Please grade this post if you find it useful.
New Member

Re: Problem creating subinterface

Hi Peter and Ivan

Thanks for your replies. It's always fun to learn new stuff.

I executed the "show idb" command and got the following output from switch A (the "bad" one):

Maximum number of Software IDBs 12000.  In use 187.

                       HWIDBs     SWIDBs

Active                     57        180

Inactive                    6          7

Total IDBs                 63        187

Size each (bytes)        3400       1256

Total bytes            214200     234872

The same command on switch B:

Maximum number of Software IDBs 12000.  In use 228.

                       HWIDBs     SWIDBs

Active                     98        219

Inactive                    6          9

Total IDBs                104        228

Size each (bytes)        3400       1256

Total bytes            353600     286368

According to this there should be no problem adding subinterfaces.

I also executed the "show platform hardware lif l2 mem" command.

Output from switch A:

Free LDB memory: 2017

Output from switch B:

Free LDB memory: 34732

Here there is a remarkable difference and it certainley seems to be low on switch A. But I don't understand why as there are more interfaces on switch B.

I also tried creating a few subinterfaces just to see if it would change the free ldb memory value. But it didn't. there was still 34732.

So I'm still a bit confused

Best regards

Thomas

New Member

Re: Problem creating subinterface

Was doing some testing and it appears that the log entry does not happen untill I execute the encapsulation command:

ISI-CORE(config)#inter g2/48.477

ISI-CORE(config-subif)#

ISI-CORE(config-subif)#encap dot 477

ISI-CORE(config-subif)#

*Aug  1 14:29:33.304 CET+1: %EARL-2-LDB_OUT_OF_RESOURCE: Out Of LDB resources. A

llocate 4096 entries failed.

Aug  1 14:29:33.308 CET+1: %EARL-DFC2-2-LDB_OUT_OF_RESOURCE: Out Of LDB resource

s. Allocate 4096 entries failed.

New Member

Hi Thomas,we have found a

Hi Thomas,

I found a solution to this problem and verified it's working with 6509-E Sup2T VSS. Please see my other comment to understand how memory for subinterfaces is allocated.

There are undocumented commands for Sup2T:
platform sub-interface maximum-vlan vland-id <count>
platform sub-interface maximum-vlan enable

These commands limit the maximum number of subinterfaces per one interface. When you enter these commands, IOS tells you how many interfaces with subinterfaces can be used. Then a reload is needed.

E.g. when you enter platform sub-interface maximum-vlan vlan-id 1000, then 92 interfaces with subinterfaces can be used (4-times more than the default number).

CENTRAL#sh platform sub-interface maximum-vlan ?
  status  status of maximum VLAN id for Layer3 sub-interfaces

CENTRAL#sh platform sub-interface maximum-vlan status
Maximum VLAN ID limit for Layer3 sub-interfaces status: enabled
Maximum VLAN ID for Layer3 sub-interfaces limit:        1000

CENTRAL#sh platform hard lif l2 memory
Free LDB memory: 59150

We have 32 active routed interfaces with 3 subinterfaces on each of them, all the sub-/interfaces are Up and working.

New Member

Hi,by default (tested on IP

Hi,

by default (tested on IP services 151-2.SY2) the limit for standard Sup2T is 21 interfaces (± 1 depending on your configuration) with defined subinterfaces. Upon defining subinterface for the 21st interface you hit the rock bottom and it's impossible to create a subinterface for another routed interface. Only aprox. 2020 blocks of lif l2 memory are left, but 4096 blocks are needed for another interface with defined subinterface. Sup2T VSS log:

%EARL-SW2-2-LDB_OUT_OF_RESOURCE: Out Of LDB resources. Allocate 4096 entries failed.
%EARL-SW2-2-SUBINF_SHUTDOWN: Out Of LIF resources. Sub-interface shutdown. Exceeded maximum limit of 22 physcial interfaces with sub-interface configuration.

SW2_DFC4: lif_l2_swif_goingdown:cannot get idb from gid 0X108A
%EARL-SW2_DFC4-2-LDB_OUT_OF_RESOURCE: Out Of LDB resources. Allocate 4096 entries failed.
SW2_DFC1: lif_l2_swif_goingdown:cannot get idb from gid 0X108A

Confused?

I have figured out that the default allocation policy for subinterfaces works like this: when the first subinterface is defined (created and dot1q tag assigned), IOS allocates LDBs for the maximum possible number of subinterfaces for that particular interface, so memory for 4096 entries is automatically allocated. I inferred that the lif l2 memory capacity is aprox. 92k LDBs total. Watch the output of show platform hardware lif l2 memory upon creating a subinterface. 92k / 4096 is ~22, this defines the limit.

According to my tests, the memory pool for SVIs is different. There is space for 12,000 switchports, internal Vlans or Vlan interfaces as can be seen in the output of show idb command mentioned by Peter. Actually, when you convert routed port to switchport, IOS allocates one block from this IDB pool.

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