Bradcast domain se odnosi na sve uredjaje koji ce "primiti" broadcast message (npr ARP). U VLANu svi uredjaji ce morati da "obrade" ARP request bez obzira kom subnetu pripadaju (destination MAC ffff.ffff.ffff). Dakle - taj L2 broadcast.
Sve u svemu
VLAN = bradcast domain.
VLAN polje postoji samo u tag-u. VLAN polje nije obavezno u L2 enkapsulaciji. Prema dokumentaciji frejmovi se taguju
samo pre nego sto se salju kroz trunk i tag se uklanja nakon sto paket udje u sledeci switch. Kako switch barata sa frejmovima unutar switcha pre slanja kroz trunk nije jasno navedeno, nasao sam neke postove u kojima se kaze da frejmovi nisu tagovani, ali...nazalost, samo rekla - kazala, nista zvanicna dokumentacija... I double tagging i VLAN hopping attack ne idu u prilog teoriji da se iz frejmova uklanja tag (mada ni kompletno protiv), ali po onom sto sam citao u nekim postovima je da switch ima interni nacin oznacavanja frejmova dok su u switchu - jos jednom - rekla kazala, ali Cisco u okviru dokumentacije (ukljuceno u CCNA trening) tvrdi da se tag dodaje samo pre slanja kroz trunk.
Cisco dokumentacija:
Inter-Switch Link and IEEE 802.1Q Frame Format
Citat:
802.1Q is the IEEE standard for tagging frames on a trunk and supports up to 4096 VLANs. In 802.1Q, the trunking device inserts a 4-byte tag into the original frame and recomputes the frame check sequence (FCS) before the device sends the frame over the trunk link. At the receiving end, the tag is removed and the frame is forwarded to the assigned VLAN. 802.1Q does not tag frames on the native VLAN. It tags all other frames that are transmitted and received on the trunk. When you configure an 802.1Q trunk, you must make sure that you configure the same native VLAN on both sides of the trunk. IEEE 802.1Q defines a single instance of spanning tree that runs on the native VLAN for all the VLANs in the network. This is called Mono Spanning Tree (MST). This lacks the flexibility and load balancing capability of PVST that is available with ISL. However, PVST+ offers the capability to retain multiple spanning tree topologies with 802.1Q trunking.
U svakom slucaju - kreiranje dva VLANa sa istim IP address range-om je moguce i svaki je zaseban broadcast domen u okviru jednog switcha. Nakon toga sto dva vlana mogu da imaju isti IP address range na jednom switchu i podataka iz zvanicne Cisco dokumentacije ostaje nejasno kako se "odradjuje" interno forwardovanje frame-ova u okviru samog switcha.
Citat:
To sto kazes za DHCP je tacno, ali je fazon (bar meni bilo interesantno) razumeti zasto tj. kako ruter zna koji opseg je za koji vlan
Dakle zarazen si - dobro dosao u klub... spremaj CCNP/CCIE
[Ovu poruku je menjao NikoVazan dana 22.12.2016. u 08:26 GMT+1]
Jedan server na 4 VLAN mreze
