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I am running OpenSUSE.

Here is the output of ssh -vvv:

OpenSSH_5.8p1, OpenSSL 1.0.0c 2 Dec 2010 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug2: ssh_connect: needpriv 0 debug1: Connecting to <ipaddress> [ipaddress] port 22. debug1: Connection established. debug1: permanently_set_uid: 0/0 debug3: Incorrect RSA1 identifier debug3: Could not load "/root/.ssh/id_rsa" as a RSA1 public key debug2: key_type_from_name: unknown key type '-----BEGIN' debug3: key_read: missing keytype debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug2: key_type_from_name: unknown key type '-----END' debug3: key_read: missing keytype debug1: identity file /root/.ssh/id_rsa type 1 debug1: identity file /root/.ssh/id_rsa-cert type -1 debug1: identity file /root/.ssh/id_dsa type -1 debug1: identity file /root/.ssh/id_dsa-cert type -1 debug1: identity file /root/.ssh/id_ecdsa type -1 debug1: identity file /root/.ssh/id_ecdsa-cert type -1 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.1 debug1: match: OpenSSH_5.1 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.8 debug2: fd 3 setting O_NONBLOCK debug3: load_hostkeys: loading entries for host "ipaddress" from file "/root/.ssh/known_hosts" debug3: load_hostkeys: found key type RSA in file /root/.ssh/known_hosts:4 debug3: load_hostkeys: loaded 1 keys debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],ssh-rsa debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug2: kex_parse_kexinit: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1 debug2: kex_parse_kexinit: [email protected],[email protected],ssh-rsa,[email protected],[email protected],[email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-dss debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected] debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: none,[email protected],zlib debug2: kex_parse_kexinit: none,[email protected],zlib debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: first_kex_follows 0 debug2: kex_parse_kexinit: reserved 0 debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1 debug2: kex_parse_kexinit: ssh-rsa,ssh-dss debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,[email protected],aes128-ctr,aes192-ctr,aes256-ctr debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,[email protected],aes128-ctr,aes192-ctr,aes256-ctr debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: none,[email protected] debug2: kex_parse_kexinit: none,[email protected] debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: debug2: kex_parse_kexinit: first_kex_follows 0 debug2: kex_parse_kexinit: reserved 0 debug2: mac_setup: found hmac-md5 debug1: kex: server->client aes128-ctr hmac-md5 none debug2: mac_setup: found hmac-md5 debug1: kex: client->server aes128-ctr hmac-md5 none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug2: dh_gen_key: priv key bits set: 138/256 debug2: bits set: 529/1024 debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Server host key: RSA cb:7f:ff:2e:65:28:f0:95:e6:8a:71:24:2a:67:02:2b debug3: load_hostkeys: loading entries for host "<ipaddress>" from file "/root/.ssh/known_hosts" debug3: load_hostkeys: found key type RSA in file /root/.ssh/known_hosts:4 debug3: load_hostkeys: loaded 1 keys debug1: Host '<ipaddress>' is known and matches the RSA host key. debug1: Found key in /root/.ssh/known_hosts:4 debug2: bits set: 504/1024 debug1: ssh_rsa_verify: signature correct debug2: kex_derive_keys debug2: set_newkeys: mode 1 debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug2: set_newkeys: mode 0 debug1: SSH2_MSG_NEWKEYS received debug1: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug2: service_accept: ssh-userauth debug1: SSH2_MSG_SERVICE_ACCEPT received debug2: key: /root/.ssh/id_rsa (0xb789d5c8) debug2: key: /root/.ssh/id_dsa ((nil)) debug2: key: /root/.ssh/id_ecdsa ((nil)) debug1: Authentications that can continue: publickey,keyboard-interactive debug3: start over, passed a different list publickey,keyboard-interactive debug3: preferred publickey,keyboard-interactive,password debug3: authmethod_lookup publickey debug3: remaining preferred: keyboard-interactive,password debug3: authmethod_is_enabled publickey debug1: Next authentication method: publickey debug1: Offering RSA public key: /root/.ssh/id_rsa debug3: send_pubkey_test debug2: we sent a publickey packet, wait for reply 

It hangs here for a good 30 seconds to a minute then

debug1: Authentications that can continue: publickey,keyboard-interactive debug1: Trying private key: /root/.ssh/id_dsa debug3: no such identity: /root/.ssh/id_dsa debug1: Trying private key: /root/.ssh/id_ecdsa debug3: no such identity: /root/.ssh/id_ecdsa debug2: we did not send a packet, disable method debug3: authmethod_lookup keyboard-interactive debug3: remaining preferred: password debug3: authmethod_is_enabled keyboard-interactive debug1: Next authentication method: keyboard-interactive debug2: userauth_kbdint debug2: we sent a keyboard-interactive packet, wait for reply debug2: input_userauth_info_req debug2: input_userauth_info_req: num_prompts 1 

I added PubkeyAuthentication no to the /etc/ssh/ssh_config and the /etc/ssh/sshd_config which makes it faster getting to the password prompt, but the password prompt still takes some time. Any way to fix that?

Here is where the password hangs

debug3: packet_send2: adding 32 (len 25 padlen 7 extra_pad 64) debug2: input_userauth_info_req debug2: input_userauth_info_req: num_prompts 0 debug3: packet_send2: adding 48 (len 10 padlen 6 extra_pad 64) debug1: Authentication succeeded (keyboard-interactive). Authenticated to ipaddress ([ipaddress]:22). debug1: channel 0: new [client-session] debug3: ssh_session2_open: channel_new: 0 debug2: channel 0: send open debug1: Requesting [email protected] debug1: Entering interactive session. 

FIXED!!!!!!!!!!!!!! What is did... In the nsswitch_conf I had ldap included in the group and passwd which slows it down a lot. Thank you everybody for your input

passwd: compat group: files hosts: files dns networks: files dns 
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    tried turning off reverse lookups in the sshd config ? that'd be my first thing to try. Commented Aug 15, 2011 at 12:43
  • Anything in the logs? Any way to get a network traffic dump of what's going on in the pause? SSH debug mode output? Anything in the LDAP server logs, or sniffing traffic on the LDAP port of what's happening from your client's IP? Commented Aug 15, 2011 at 13:01
  • I added useDNS no in the /etc/sh/ssh_config and that didn't seem to help either Commented Aug 15, 2011 at 13:04
  • there is nothing in the logs that I can see. The /var/log/messages is clean Commented Aug 15, 2011 at 13:06
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    @johnathon Please add your answer to this question and accept it so it doesn't appear in the unanswered lists. Commented Aug 16, 2011 at 12:48

3 Answers 3

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Your ssh client might be trying GSSAPIAuthentication, which takes 30 seconds to timeout. You can disable that in your .ssh/config file with

Host example.org GSSAPIAuthentication no 

If that does not help, use -v or -vvv to get debug information.


When it hangs at public key authentication - and you don't use public keys - also disable that:

PubkeyAuthentication no 
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  • That is already commented out but I uncommented and it still is slow... Commented Aug 15, 2011 at 12:54
  • I just added that, restarted ssh and it still hangs at the "we sent a public key packet, wait for reply" Commented Aug 15, 2011 at 13:11
  • I mean ~/.ssh/config - not the sshD config Commented Aug 15, 2011 at 13:28
  • all that is under ~/.ssh is known hosts this is the file that I was editing vi /etc/ssh/ssh_config Commented Aug 15, 2011 at 13:32
  • Then create the file. Commented Aug 15, 2011 at 13:54
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I have previously experienced something similar that was a result of setting the search scope to "sub" rather than scope of "base", because sub will do a full tree search if you set the base to your root like "dc=example,dc=com", and the scope to -s sub

If you try the test from the command line with -s set to base rather than sub you get a much faster query...

 time ldapsearch -D "cn=directory manager" -w secret -p 389 \ -h server.example.com -b "dc=example,dc=com" -s sub "(objectclass=*)" 

and then try again with the scope as base

time ldapsearch -D "cn=directory manager" -w secret -p 389 \ -h server.example.com -b "" -s base "objectclass=*" 
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There are a handful of issues which might cause slowness in ssh / sudo authentications.

Most recently, we were experiencing really slow SSH authentications for Active Directory logins on a Realm domain joined Linux host, where the domain controller was on a separate VLAN.

Almost anything which required domain authentication was really slow and caused a lot of frustration.

To troubleshoot we ran port scan, helping us determine that the LDAP query across VLAN was passing through our firewall but a firewall flag to allow LDAP was not properly configured. Additionally this was attempting to run over port 3268 for Global Catalogue which would always timeout (hence the really long login times).

We got to this solution based on a helpful reddit thread with various suggestions here

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