Cisco – SSH failing from Cisco routers to Dell switches

Running into two separate but probably similar issues.

First issue –

I have two Cisco 2900 Series routers on firmware v15.2(4)M4 trying to ssh into a Dell 5548P stack on firmware v4.1.0.8. All attempts fail instantly with –

router#ssh 1.2.3.4
[Connection to 1.2.3.4 aborted: error status 0]

Buffer log shows –

SSH2 CLIENT 0: Server has chosen 2056 -bit dh keys
%SSH-3-INV_MOD: Invalid modulus length

If I try to modify the DH key length on the router, attempts still fail and buffer log shows –

SSH2 CLIENT 0: Server has chosen 2056 -bit dh keys
%SSH-3-INV_MOD: Invalid modulus length  
%SSH-3-DH_RANGE_FAIL: Client DH key range mismatch with maximum configured DH key on server

SSH config on router –

SSH Enabled - version 2.0
Authentication timeout: 120 secs; Authentication retries: 3
Minimum expected Diffie Hellman key size : 1024 bits
IOS Keys in SECSH format(ssh-rsa, base64 encoded):
ssh-rsa keystringgoeshere

SSH config on 5548P stack –

SSH Server enabled. Port: 22
RSA key was generated.
DSA(DSS) key was generated.
SSH Public Key Authentication is disabled.

There don't seem to be any in-depth settings related to the ssh server here that I can modify.

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Second issue –

I have another two Cisco 2900 Series routers at a different site on firmware v15.4(3)M3 trying to ssh into a Dell N1548P stack on firmware v6.3.0.6. All attempts fail with –

router#ssh 5.6.7.8
Password:
[Connection to 5.6.7.8 aborted: error status 0]

Buffer log shows –

SSH2 CLIENT 0:  Channel open failed, reason = 1752134516

SSH config on router –

SSH Enabled - version 2.0
Authentication methods:publickey,keyboard-interactive,password
Encryption Algorithms:aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
MAC Algorithms:hmac-sha1,hmac-sha1-96
Authentication timeout: 120 secs; Authentication retries: 3
Minimum expected Diffie Hellman key size : 1024 bits
IOS Keys in SECSH format(ssh-rsa, base64 encoded):
ssh-rsa keystringgoeshere

SSH config on N1548P stack –

SSH Server enabled.  Port: 22
Protocol Levels: Versions 1 and 2.
SSH Connections Currently in Use: ............. 1
Maximum number of SSH Sessions Allowed: ....... 5
SSH Session Timeout: .......................... 600
RSA key was generated.
DSA key was generated.
SSH Public Key Authentication is disabled.

In this particular scenario, if I modify the router to use SSH v1, it's able to connect. Using v2, it's not. Of course, we don't want to use v1. I haven't been able to figure out what reason "1752134516" means.

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Note that I'm able to SSH into both switch stacks directly. It's only the routers that aren't able to connect.

Thanks for any help.