How to support vendor in dpd?

["=?GB2312?Q?=C2=ED=D4=C6=DD=BA?=" <mayy@i-net.com.cn>]

Hi,
	According to draft-ietf-ipsec-dpd-02.txt, the vendor ID describe here is "HASHED_VENDOR_ID = {0xAF, 0xCA, 0xD7, 0x13, 0x68, 0xA1, 0xF1,0xC9, 0x6B, 0x86, 0x96, 0xFC, 0x77, 0x57}". But cisco router changes vendor id  every time. Why?