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Vlan discovery per dhcp, Dhcp support explanation of option 43 – Siemens HIPATH 8000 User Manual

Page 39

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Technical Overview

39

VLAN discovery per DHCP

An additional use for DHCP in the phone is the Æ VLAN discovery per

DHCP feature. This allows the phone to discover its VLAN from a DHCP

server in the untagged LAN. After discovering its VLAN the phone starts

its standard DHCP process within that discovered VLAN to configure itself

from the DHCP within that VLAN.

DHCP Support Explanation of Option 43

As no DHCP option exists for the exchange of VLAN information over

DHCP, the Vendor Specific Information option (43) shall be used to encap-

sulate VLAN and download configuration. The following diagram illustrates

the format of the Vendor Specific Option.

Byte 1 contains the tag "43", option 1 data contains the "Siemens" identifier

and the VLAN ID is contained in option 2. Five Padding Bytes starting in

Byte 20 and the terminate option 255 in byte 25 complete the option

frame.

If you have to specify a configuration download server for configuration up-

date ( see Æ page 88) so you have to add the values of the server. You can

place the new option before or after the VLAN information but the five Pad-

ding Bytes (Value 0) and the terminate option 255 have to close the op-

tion frame.

Example:

Code: 3

length: 28

data: sdlp://dls.siemens.com:18443

The five Padding Bytes and the terminate option 255 now completes

the option frame in byte 48.

SIP Server option 120:

Because the phone only reads the first name/IP address supplied in

option 120, the maximum length of the contents has been limited

to 50 octets. Please be aware of this when you are using it.

Byte #

0 1 2 3 4

5

6

7

8

9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Descrip-

tion

Co

de

Le

ng

th

Co

de

Le

ng

th Option 1 data - "Siemens" identifier

Co

de

Le

ng

th Option 2 data -

to be allocated

VID

P

addi

ng

P

addi

ng

P

addi

ng

P

addi

ng

P

addi

ng

Co

de

Value

43 20 1 10 ’S’ ’i’ ’e’ ’m’ ’e’ ’n’ ’s’ 0

0

0

2 4 0 0

VID HI

VID L

O 0

0

0

0

0

255

20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55

Co

de

Le

ngt

h Option 1 data - "dls server address"

P

addin

g

P

addin

g

P

addin

g

P

addin

g

P

addin

g

Co

de

3 28 ’s’ ’d’ ’l’ ’p’ ’:’ ’/’ ’/’ ’d’ ’l’ ’s’ ’.’

’s’ ’i’ ’e’ ’m’ ’e’ ’n’ ’s’ ’.’

’c’ ’o’ ’m’ ’:’ ’1’ ’8’ ’4’ ’4’ ’3’ 0

0

0

0

0

255