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My supervisor told me to go to the server room and connect a bunch of servers to the Department network so they are accessible from office PCs. In the server room we have 7 servers, a couple of wall jacks and a couple of switches. I only use one wall jack.

First thing I tried was using a simple D-Link DGS 105 switch by connecting one of its ports to the wall jack and connected two servers to two other ports. Both the servers obtained IP address and things seemed to be working fine. But There are 7 servers each having at least 5 interfaces so that 5 port D-Link switch is not going to suffice. Besides, there are these shiny beautiful Aruba switches (2530 and 2930F) that are just sitting there so I figured I would use those. The objective is to add my servers to the same LAN segment as the default gateway and be able to communicate with them directly using the PC's in the offices.

I did the same thing with one Aruba switch. I connected port 1 to the wall, and the two servers to ports 3 and 5 all on vlan 1 all untagged. Here is what happens: When IP address setting is set to bootp/dhcp on vlan 1, the switch SVI obtains and IP address but none of the servers do. I have mirrored port 1 traffic and captured DHCP frames, the broadcasts are being sent out of port 1 into the wall but no reply or offer comes back in. When I disable IP address and IP routing on the switch, one of the servers is able to obtain an IP address but the other(s) don't. They keep broadcasting DHCP discovers but no reply comes back. The default gateway address is on a different subnet from the DHCP server address which I saw in DHCP ACKs so I think the default gateway behind the wall already has dhcp-relay enabled. By the way, all outbound Ethernet frames of port 1 have the VLAN tag with VID = 1 but no Inbound traffic has VLAN tags neither the DHCP replies (when it works for one server) nor the DHCP broadcasts of other devices behind the wall.

DHCP-snooping is disabled on the switch. I have checked the MAC address table of the switch and everything seems to be correct. There are lots of different entries for interface 1 and the correct server MAC addresses for port 3 and 5.

My Question: Why is the behaviour different with the Aruba switch? How can I just connect my servers to the same LAN segment as the D-Link switch seems to be doing? Does it have something to do with port security? If so why isn't the D-Link switch having any issues? Am I on the right track? Is the basic setup I am looking for even possible?

Unfortunately I don't have access to whatever is behind the wall, like DHCP server logs, as that is managed by department IT.

output of show config:

hostname "Aruba-2930F-48G-4SFPP"                                                
module 1 type jl254a                                                            
mirror 1 port 2                                                                 
no dhcp-relay                                                                   
no ip icmp redirects                                                            
ip route 0.0.0.0 0.0.0.0 10.172.156.1 metric 250                                
interface 1                                                                     
   monitor all both mirror 1                                                    
   exit                                                                         
snmp-server community "public" unrestricted                                     
vlan 1                                                                          
   name "DEFAULT_VLAN"                                                          
   no untagged 2                                                                
   untagged 1,3-52                                                              
   no ip address                                                                
   ip helper-address 10.59.232.5                                                
   exit                                                                         
vlan 2                                                                          
   name "MONITOR"                                                               
   untagged 2                                                                   
   no ip address                                                                
   exit                                                                         
                                                                                                                                                    

vlan 1 info:

    VLAN ID : 1                                                                   
  Name : DEFAULT_VLAN                                                           
  Status : Port-based                                                           
  Voice : No                                                                    
  Jumbo : No                                                                    
  Private VLAN : none                                                           
  Associated Primary VID : none                                                 
  Associated Secondary VIDs : none                                              
                                                                                
  Port Information Mode     Unknown VLAN Status                                 
  ---------------- -------- ------------ ----------                             
  1                Untagged Learn        Up                                     
  3                Untagged Learn        Up                                     
  4                Untagged Learn        Down                                   
  5                Untagged Learn        Up                                     
  6                Untagged Learn        Down                                   
  7                Untagged Learn        Down                                   
  8                Untagged Learn        Down                                   
  9                Untagged Learn        Down                                   
  10               Untagged Learn        Down  

                             
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  • Please add the configurations of your Aruba switches to your question (in text format, using the editor's {} preformat option). We cannot simply guess what went wrong.
    – Zac67
    Oct 12, 2023 at 18:54
  • 1
    You seem to have an IT department... why are they not helping you deploy your IT stuff? Oct 12, 2023 at 19:56
  • I have been trying to communicate with them. They're not very responsive.
    – Amjal
    Oct 12, 2023 at 20:22
  • I'm afraid networks not under your control are explicitly off topic here, see the help center. If you can't get them on board we need to close your question.
    – Zac67
    Oct 13, 2023 at 12:43

1 Answer 1

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That switch has two port-based (untagged) VLANs configured. Each VLAN acts like a separate switch.

Port 2 connects to VLAN 2, leading nowhere. Anything you connect there gets a physical link but it doesn't lead anywhere - looks pretty useless.

The other ports connect directly to VLAN 1. Anything connected to those ports can talk to each other.

However, there's an IP helper configured, intercepting DHCP discover and request packets, and sending them to the DHCP server at 10.59.232.5. Accordingly, any DHCP client gets its IP config from that server (or not).

In contrast, any host connected directly to your uplink or through a simple, unmanaged switch runs DHCP directly on VLAN 1. If that works and the IP helper method doesn't, you need to remove that config from the switch (no vlan 1 ip helper-address). While you're at it you might want to remove VLAN 2 from the switch as well.

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  • Thanks for the answer man. The reason for creating vlan 2 was isolating the mirror port from the rest of the network. So if I am interested in the traffic of port 1 only, I would not receive the broadcasts of port 3 and 5. Does that make sense to you? Maybe there is a better way to do it. But I will delete it after this perhaps. Anyway, I thought the ip-helper config wouldn't have effect when dhcp-relay is disabled. I went ahead and disabled ip-helper anyways but the issue persists.
    – Amjal
    Oct 12, 2023 at 21:20
  • For general troubleshooting, your should check the switch's MAC address table to see whether hosts are in the VLAN that you expect. If all that looks OK then the problem is the uplink port. Examples include LLDP monitoring, BPDU monitoring (STP doesn't seem to be active), or MAC-based port-level authentication.
    – Zac67
    Oct 13, 2023 at 12:40

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