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OpenSSH Issue

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Thiru:
Good day All,

My first post, and a very strange one.

I have installed 4 new LPARs on a p570 box.
All having similar resources, OS and apps.

- AIX 5300-10-01-0921
- OpenSSH_5.0p1, OpenSSL 0.9.8k-fips 25 Mar 2009

I am having 2 strange problems, all pertaining to SSH.
All problems seem to only be between LPARs 1; 2 & 3.
LPAR 4 seems fine.
LPAR 1 & 4 are DB2 servers, and LPAR's 2 & 3 are WAS Servers.

1.

--- Quote --- Specifying a BANNER in /etc/ssh/sshd_config causes the login prompt to hang when trying to ssh between the LPARs.
Removing it also removes this problem.

--- End quote ---

2.

--- Quote ---SCP between LPARs don't work, it just stalls.
The first file is created on the target server with a size of 0, but you have to eventually cancel.

[u3tm3] /tmp/ssh/tn # scp u3tm:/tmp/ssh/* .
root@u3tm's password:
gskjs.rte                                       0%    0     0.0KB/s - stalled -

Only works fine if they are copying between LPAR 4

--- End quote ---

I have uninstalled and re-installed SSL & SSH, but nothing works.
I have no idea why this problem is not occuring on LPAR 4.

Thiru:
There is also a 3rd issue.

If I ssh to LPAR1, then to LPAR2, and try to vi a file or open smitty . . . . it hangs, and eventually timesout and closes connection back to LPAR1. :o

Thiru:
OK, I figured out the problem  :-X

I had configured Etherchannel on the first 3 LPARs.
I did not configure it on LPAR 4 as yet, so that got me thinking it was the Etherchannel.
I configured them with Standard mode, but I changed it to use JUMBO FRAMES.
Once I changed JUMBO FRAMES to NO, problem solved.

Since JUMBO FRAMES changes the MTU from 1500 to 9000, I guess the switch then needs to be configured to allow this.

I hope someone else has also been able to learn from this.

 ;D

Michael:
You have certainly given us all something to remember. Out of curiosity - where there any entries in the errlog about MTU mismatches, and/or netstat -v (or entstat -d entX).

Thanks for the full report!

Thiru:
I see no errors in the errorlog, and did not check netstat before i corrected the problem.

But I noticed, that athough I switched Jumbo Frames to NO,if I do a entstat, it says Jumbo Frames Enabled?

EtherChannel Attributes:

--- Quote ---EtherChannel / Link Aggregation: ent3
Status: Available
Attributes:
      adapter_names   ent0           EtherChannel Adapters
      alt_addr        0x000000000000 Alternate EtherChannel Address
      auto_recovery   yes            Enable automatic recovery after failover
      backup_adapter  ent1           Adapter used when whole channel fails
      hash_mode       default        Determines how outgoing adapter is chosen
      mode            standard       EtherChannel mode of operation
      netaddr         0              Address to ping
      noloss_failover yes            Enable lossless failover after ping failure
      num_retries     3              Times to retry ping before failing
      retry_time      1              Wait time (in seconds) between pings
      use_alt_addr    no             Enable Alternate EtherChannel Address
      use_jumbo_frame no             Enable Gigabit Ethernet Jumbo Frames


--- End quote ---


entstat output:

--- Quote ----------------------------------------------------------------
ETHERNET STATISTICS (ent3) :
Device Type: EtherChannel
Hardware Address: 00:14:5e:47:a3:10
Elapsed Time: 0 days 20 hours 10 minutes 25 seconds

Transmit Statistics:                          Receive Statistics:
--------------------                          -------------------
Packets: 1932476                              Packets: 2166445
Bytes: 144108349                              Bytes: 449085723
Interrupts: 0                                 Interrupts: 1518927
Transmit Errors: 0                            Receive Errors: 0
Packets Dropped: 0                            Packets Dropped: 0
                                              Bad Packets: 0
Max Packets on S/W Transmit Queue: 10
S/W Transmit Queue Overflow: 0
Current S/W+H/W Transmit Queue Length: 2

Elapsed Time: 0 days 0 hours 0 minutes 0 seconds
Broadcast Packets: 2464                       Broadcast Packets: 128669
Multicast Packets: 581                        Multicast Packets: 1162
No Carrier Sense: 0                           CRC Errors: 0
DMA Underrun: 0                               DMA Overrun: 0
Lost CTS Errors: 0                            Alignment Errors: 0
Max Collision Errors: 0                       No Resource Errors: 0
Late Collision Errors: 0                      Receive Collision Errors: 0
Deferred: 0                                   Packet Too Short Errors: 0
SQE Test: 0                                   Packet Too Long Errors: 0
Timeout Errors: 0                             Packets Discarded by Adapter: 0
Single Collision Count: 0                     Receiver Start Count: 0
Multiple Collision Count: 0
Current HW Transmit Queue Length: 2

General Statistics:
-------------------
No mbuf Errors: 0
Adapter Reset Count: 0
Adapter Data Rate: 2000
Driver Flags: Up Broadcast Running
        Simplex 64BitSupport ChecksumOffload
        PrivateSegment LargeSend DataRateSet

=============================================================
=============================================================

Statistics for every adapter in the EtherChannel:
-------------------------------------------------

Number of adapters: 2
Active channel: primary channel
Operating mode: Network interface backup mode

-------------------------------------------------------------

ETHERNET STATISTICS (ent0) :
Device Type: 2-Port 10/100/1000 Base-TX PCI-X Adapter (14108902)
Hardware Address: 00:14:5e:47:a3:10

Transmit Statistics:                          Receive Statistics:
--------------------                          -------------------
Packets: 1932512                              Packets: 2100051
Bytes: 144113833                              Bytes: 442340949
Interrupts: 0                                 Interrupts: 1453696
Transmit Errors: 0                            Receive Errors: 0
Packets Dropped: 0                            Packets Dropped: 0
                                              Bad Packets: 0
Max Packets on S/W Transmit Queue: 9
S/W Transmit Queue Overflow: 0
Current S/W+H/W Transmit Queue Length: 1

Broadcast Packets: 2464                       Broadcast Packets: 63103
Multicast Packets: 581                        Multicast Packets: 581
No Carrier Sense: 0                           CRC Errors: 0
DMA Underrun: 0                               DMA Overrun: 0
Lost CTS Errors: 0                            Alignment Errors: 0
Max Collision Errors: 0                       No Resource Errors: 0
Late Collision Errors: 0                      Receive Collision Errors: 0
Deferred: 0                                   Packet Too Short Errors: 0
SQE Test: 0                                   Packet Too Long Errors: 0
Timeout Errors: 0                             Packets Discarded by Adapter: 0
Single Collision Count: 0                     Receiver Start Count: 0
Multiple Collision Count: 0
Current HW Transmit Queue Length: 1

General Statistics:
-------------------
No mbuf Errors: 0
Adapter Reset Count: 1
Adapter Data Rate: 2000
Driver Flags: Up Broadcast Running
        Simplex 64BitSupport ChecksumOffload
        PrivateSegment LargeSend DataRateSet

2-Port 10/100/1000 Base-TX PCI-X Adapter (14108902) Specific Statistics:
------------------------------------------------------------------------
Link Status : Up
Media Speed Selected: Auto negotiation
Media Speed Running: 1000 Mbps Full Duplex
PCI Mode: PCI-X (100-133)
PCI Bus Width: 64-bit
Latency Timer: 144
Cache Line Size: 128
Jumbo Frames: Enabled
TCP Segmentation Offload: Enabled
TCP Segmentation Offload Packets Transmitted: 390
TCP Segmentation Offload Packet Errors: 0
Transmit and Receive Flow Control Status: Enabled
XON Flow Control Packets Transmitted: 0
XON Flow Control Packets Received: 0
XOFF Flow Control Packets Transmitted: 0
XOFF Flow Control Packets Received: 0
Transmit and Receive Flow Control Threshold (High): 24576
Transmit and Receive Flow Control Threshold (Low): 16384
Transmit and Receive Storage Allocation (TX/RX): 24/40

-------------------------------------------------------------
Backup adapter - ent1:
======================

ETHERNET STATISTICS (ent1) :
Device Type: 2-Port 10/100/1000 Base-TX PCI-X Adapter (14108902)
Hardware Address: 00:14:5e:47:a3:10

Transmit Statistics:                          Receive Statistics:
--------------------                          -------------------
Packets: 0                                    Packets: 66397
Bytes: 0                                      Bytes: 6744954
Interrupts: 0                                 Interrupts: 65233
Transmit Errors: 0                            Receive Errors: 0
Packets Dropped: 0                            Packets Dropped: 0
                                              Bad Packets: 0
Max Packets on S/W Transmit Queue: 1
S/W Transmit Queue Overflow: 0
Current S/W+H/W Transmit Queue Length: 1

Broadcast Packets: 0                          Broadcast Packets: 65566
Multicast Packets: 0                          Multicast Packets: 581
No Carrier Sense: 0                           CRC Errors: 0
DMA Underrun: 0                               DMA Overrun: 0
Lost CTS Errors: 0                            Alignment Errors: 0
Max Collision Errors: 0                       No Resource Errors: 0
Late Collision Errors: 0                      Receive Collision Errors: 0
Deferred: 0                                   Packet Too Short Errors: 0
SQE Test: 0                                   Packet Too Long Errors: 0
Timeout Errors: 0                             Packets Discarded by Adapter: 0
Single Collision Count: 0                     Receiver Start Count: 0
Multiple Collision Count: 0
Current HW Transmit Queue Length: 1

General Statistics:
-------------------
No mbuf Errors: 0
Adapter Reset Count: 1
Adapter Data Rate: 2000
Driver Flags: Up Broadcast Running
        Simplex 64BitSupport ChecksumOffload
        PrivateSegment LargeSend DataRateSet

2-Port 10/100/1000 Base-TX PCI-X Adapter (14108902) Specific Statistics:
------------------------------------------------------------------------
Link Status : Up
Media Speed Selected: Auto negotiation
Media Speed Running: 1000 Mbps Full Duplex
PCI Mode: PCI-X (100-133)
PCI Bus Width: 64-bit
Latency Timer: 144
Cache Line Size: 128
Jumbo Frames: Enabled
TCP Segmentation Offload: Enabled
TCP Segmentation Offload Packets Transmitted: 0
TCP Segmentation Offload Packet Errors: 0
Transmit and Receive Flow Control Status: Enabled
XON Flow Control Packets Transmitted: 0
XON Flow Control Packets Received: 0
XOFF Flow Control Packets Transmitted: 0
XOFF Flow Control Packets Received: 0
Transmit and Receive Flow Control Threshold (High): 24576
Transmit and Receive Flow Control Threshold (Low): 16384
Transmit and Receive Storage Allocation (TX/RX): 24/40

--- End quote ---

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