Because you're breaking the Layer 2 functionality. So there isn't anything wrong with a L3 link, but you need to add other SVI's for the other VLANs, and have routing actually work between them.
L2 requires spanning tree for magic to happen. L3 requires routing for magic to happen. HTH, Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE-M #153, CISSP, et al. CCSI/JNCI-M/JNCI-ER VP - Technical Training - IPexpert, Inc. IPexpert Sr. Technical Instructor A Cisco Learning Partner - We Accept Learning Credits! [EMAIL PROTECTED] Telephone: +1.810.326.1444 Fax: +1.810.454.0130 http://www.ipexpert.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jack Poon Sent: Saturday, October 13, 2007 6:11 AM To: [email protected] Subject: [OSL | CCIE_RS] Bridge and Switch Hi all, Consider a special scenario.... 4 x 3560, has link physically connected. Cat1 port 23 <--> Cat2 port 23 Cat1 port 24 <--> Cat2 port 24 Cat2 port 19 <--> Cat3 port 19 Cat3 port 23 <--> Cat4 port 23 Cat3 port 24 <--> Cat4 port 24 And configure trunk link as follows: Cat1 <--> Cat2 <--> Cat3 <--> Cat4 when Cat2 and Cat3 communicate using routed ports, it cannot get thru... Cat2 .....Cat1 <--> Cat2 <--> Cat3 <--> Cat4 ..... Cat3 ..... means routed port (Cat2, Cat3 Routed port, Cat1, Cat4 access port) <--> means trunk link. So, what is the reason, why it cannot work? Configuration as follows Cat1: vtp mode transp vlan 123 int f0/23 desc trunk Cat1 to Cat2 switchport trunk enc dot1q switchport mode trunk no shut int f0/24 desc access port attach Cat2 switchport mode access switchport access vlan 123 no shut Cat2: vtp mode transp vlan 123 int f0/23 desc trunk Cat2 to Cat1 switchport trunk enc dot1q switchport mode trunk no shut int f0/24 desc routed port to Cat1 no switchport ip addr 1.1.1.2 255.255.255.0 no shut int f0/19 desc trunk Cat2 to Cat3 switchport trunk enc dot1q switchport mode trunk no shut Cat3: vtp mode transp vlan 123 int f0/19 desc trunk Cat3 to Cat2 switchport trunk enc dot1q switchport mode trunk no shut int f0/23 desc trunk Cat3 to Cat4 switchport trunk enc dot1q switchport mode trunk no shut int f0/24 desc routed port to Cat4 no switchport ip addr 1.1.1.3 255.255.255.0 no shut Cat4: vtp mode transp vlan 123 int f0/23 desc trunk Cat4 to Cat3 switchport trunk enc dot1q switchport mode trunk no shut int f0/24 desc access port attach Cat3 switchport mode access switchport access vlan 123 no shut
