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I have a UPS device connected to a Juniper EX switch. According to the UPS device documentation the device used DHCP and BOOTP to obtain a IP. This is part of a management network which doesn't have a DHCP or BOOTP Server.

With wireshark I can see the BOOTP messages from the UPS device on a laptop connected to the same switch. I tried making a static arp entry in windows laptop I used run wireshark, which is also suggested in the documentation.

arp -s 10.10.12.3 00-c0-b7-xx-xx-xx

My laptop network is set to 10.10.12.2/ 255.255.255.0. When I try to ping, ssh, telnet that IP of the new ARP entry I don't get a response. If I connect directly to the device, with the arp entry intact, I get no response.

Without setting up a DHCP, or BOOTP, server what other options do I have to get telnet/ssh to a device which does not have a set IP address?

I've considered editing EX configure the interface of the UPS, but it is producing errors

[edit interfaces ge-0/0/24] #show
unit 0 {
  family inet {
    address 10.10.12.1/24 {
        arp 10.10.12.11 mac 00:c0:b7:c6:45:a3 publish;

Interface ge-0/0/24.0 not enabled for switching
error: configuration check-out failed
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  • Unfortunately, questions about host configurations are off-topic here. Unless you can get an IP address on the device, you will not be able to use any IP-based application, e.g. telnet or SSH, to access it.
    – Ron Maupin ♦
    Commented Aug 17, 2017 at 16:38
  • Adding a manual ARP entry will only work when the device doesn't care which IP is used to refer to it. Most do. Just set up a temporary DHCP server and let it get a lease, then configure a static address. Alternatively, is there a console port?.
    – Zac67 ♦
    Commented Aug 17, 2017 at 16:41
  • @Zac67 they use a RJ12 to DB9 serial to provide console. The cables wasn't in the collection here, although it should have shipped with one. Hopefully it didn't walk away too far. The temp DHCP server looks like the current winner.
    – RunThor
    Commented Aug 17, 2017 at 17:32
  • Often, devices configured for DHCP have a fallback IP address that is used when DHCP fails. This should be mentioned in the manual.
    – Zac67 ♦
    Commented Aug 17, 2017 at 17:37

2 Answers 2

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Until the device has an IP address, you will not be able to Telnet to it. While a static ARP entry may get you a mapping on the host PC, the UPS IP stack will ignore any traffic destined for an IP address it does not bind to.

You didn't mention the model, but you should be able to set up a DHCP server on most EX switch platforms (the configuration does vary a bit on the newer models).

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  • Tftpd64 (or tftpd32 if you have 32 bit) is free software you can easily put a dhcp server, sys log server, telnet client and server on a pc in a flash. Be responsible though. Don't run this software on a live network with the dhcp feature turned on.
    – Fixitrod
    Commented Aug 22, 2017 at 17:09
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I'll take some of the blame on this as I should have read the manual more closely. After putting in the ARP entry I needed to use a ping with a modified length

ping xx.xx.xx.xx -l 113

For what ever reason after doing that I was able to telnet into that same IP.

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