VLAN Trunking J9782A

Hi,

I have inherited a site with I HP network (I've always been Cisco) and have a J9782A with the following config:

running configuration:

; J9782A Configuration Editor; Created on release #YB.15.12.0006
; Ver #04:01.ff.37.27:ea
hostname "CABxxSW1"
timesync sntp
sntp unicast
sntp server priority 2 A.B.C.D
no telnet-server
ip default-gateway A.B.1.1
snmp-server community "public" unrestricted
vlan 1
name "DEFAULT_VLAN"
no untagged 1-24
tagged 25-28
ip address dhcp-bootp
exit
vlan 5
name "DATA"
untagged 5-28
ip address A.B.C.D 255.255.0.0
exit
vlan 50
name "VOICE"
tagged 25-28
no ip address
exit
vlan 51
name "FACTSYS"
untagged 1-4
tagged 25-28
no ip address
exit
vlan 250
name "GUEST"
tagged 25-28
no ip address
exit
spanning-tree
no tftp server
no dhcp config-file-update
password manager


The problem is, I cant get any VL51 traffic off the switch and cant see the vl51 devices anywhere else.

VLAN5 works fine, it's just as if 51 isnt being trunked. Am I right in thinking that UNTAGGING VLAN 5 on the uplinks (25 - 28) is the same as 'switchport trunk native vlan 5' on 25 - 28 as all the other vlans are tagged?
And that untagging 1 - 4 on VL51 is the same as 'switchport access vlan 51'?

My assumption is, for some reason the vlans arent being trunked properly. Is this down to an error in this config or should I look further up the chain for a misconfigured uplink?

Any help greatly appreciated

TIA