h1-Catos# sho port capabilities Model WS-X6K-SUP2-2GE 1000BaseSX Auto MDIX AuxiliaryVlan Broadcast suppression percentage( 100) Channel COPS port group 1/1-2 CoS rewrite Dot1q-all-tagged Dot1x Chapter 5: Trunking Duplex Fast start Flow control receive-(off,on,desired), send- (off, on, desired) Inline power Jumbo frames Link debounce timer Link debounce timer delay Membership static, dynamic Port ASIC group 1/1-2 00S scheduling rx- (1p1q4t), tx- (1p2q2t) Security source, destination Speed Sync restart delay ToS rewrite Trunk encap type 802.10, ISL Trunk mode on, off, desirable, auto, nonegotiate ISL differs from 802.1Q in a couple of ways. First, ISL is a Cisco proprietary proto- col, whereas 802.1Q is an IEEE standard. Second, ISL encapsulates Ethernet frames within an ISL frame, while 802.1 1Q alters existing frames to include VLAN tags. Fur- thermore, ISL is only capable of supporting 1,000 VLANs, while 802.1Q is capable of supporting 4,096. On switches that support both ISL and 802.1Q, either may be used. The protocol is specific to each trunk. While both sides of the trunk must agree on a protocol, you may configure ISL and 802. 1Q trunks on the same switch and in the same network. To add VLAN information to a frame to be sent over a trunk, ISL encapsulates the entire frame within a new frame. An additional header is prepended to the frame, and a small suffix is added to the end. Information regarding the VLAN number and some other information is present in the header, while a checksum of the frame is included in the footer. A high-level overview of an ISL frame is shown in Figure 5-3. Header and footer added by ISL ISL header Ethernet header TCP packet Telnet header Figure 5-3. ISL encapsulated frame The frame check sequence (FCS) footer is in addition to the FCS field already present in Ethernet frames. The ISL FCS frame computes a checksum based on the frame including the ISL header; the Ethernet FCS checksum does not include this header. How Trunks Work Adding more information to an Ethernet frame can be 