udp-helper server 10.20.0.255, is a broadcast address allowed?

Created: Feb 27, 2019 23:04:59Latest reply: Mar 1, 2019 13:52:05 207 4 0 0
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This post was last edited by BangorUni at 2019-02-28 16:16.

udp-helper enable

udp-helper port 402


vlanif 100

ip address 10.1.1.1 24

udp-helper server 10.20.255.255


1. There are many hosts on 10.20.0.0 16 (vlan 620) which all need to be sent udp 402 broadcast packets from a WoL server which lives in vlan 100 so will this work? As these PC's are asleep they do not own IP addresses so need a "magic packet" sent to vlan 620.


2. What happens to the original broadcast packet 255.255.255.255 sent from the WoL server? Is it duplicated and the duplicated packets destination is rewritten with the udp-helper server address and it still broadcasts locally within vlan 100 using 255.255.255.255 or does the switch now only use the udp-helper address and discards the original broadcast packet with destination 255.255.255.255 so it never broadcasts locally within its own vlan 100?


Hope this makes sense.


Thank you.

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Featured Answers
Created Mar 1, 2019 13:52:05 Helpful(0) Helpful(0)

@BangorUni hi, I tried with cisco on the eve-ng, and it works, but when configure the server address was configured a broadcast IP, the router should enable the directed broadcast, so that the router would forward the directed broadcast,
hope this could help you.
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  • convention:

All Answers
sim_157 Created Feb 28, 2019 14:54:03 Helpful(0) Helpful(0)

@BangorUni hi, the udp-helper server address can't be assigned a broadcast IP addrss,
about the question 2, I think the device will broadcast the packet and also forward the packet to the server .
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BangorUni Created Feb 28, 2019 16:17:43 Helpful(0) Helpful(0)

I just found this:

https://support.huawei.com/enterprise/en/doc/EDOC1000174046/8f051fab/udp-helper-configuration-commands#udp-helper_server

it states that the ip-address can be a subnet broadcast address, so 10.20.255.255 should be allowed?
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chenhui Admin Created Feb 28, 2019 17:35:19 Helpful(0) Helpful(0)

Posted by BangorUni at 2019-02-28 16:17 I just found this:https://support.huawei.com/enterprise/en/doc/EDOC1000174046/8f051fab/udp-helper-co ...
as the documentation said, the server IP address can be assigned a broadcast IP address
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Scott_Qing Created Mar 1, 2019 13:52:05 Helpful(0) Helpful(0)

@BangorUni hi, I tried with cisco on the eve-ng, and it works, but when configure the server address was configured a broadcast IP, the router should enable the directed broadcast, so that the router would forward the directed broadcast,
hope this could help you.
  • x
  • convention:

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