> For the complete documentation index, see [llms.txt](https://docs.pancakeswap.finance/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.pancakeswap.finance/chinese/jiao-yi/crosschain-swaps/swap-scenarios.md).

# 兑换场景

跨链交易有 4 种情形。

#### 1️⃣ 仅桥接（Bridge Only）

* 示例：**将 Base 上的 ETH 桥接到 Arbitrum 上的 ETH**
* 只有受支持的代币（USDC、USDT、WETH 等）才能直接桥接。这些代币因源链和目标链而异。

#### 2️⃣ 兑换 → 桥接（Swap → Bridge）

* 示例：**将 BNB Chain 上的 BNB 兑换为 Arbitrum 上的 USDC**
* 使用 BNB chain 上的 PancakeSwap 池将 BNB 兑换为受支持的桥接代币（例如 USDC）
* 通过 Across 将 USDC 桥接到 Arbitrum

#### 3️⃣ 桥接 → 兑换（Bridge → Swap）

* 示例：**将 BNB Chain 上的 USDC 兑换为 Arbitrum 上的 ARB**
* 通过 Across 桥接 USDC
* 使用 Arbitrum 上的 PancakeSwap 池将 USDC 兑换为 ARB

#### 4️⃣ 兑换 → 桥接 → 兑换（Swap → Bridge → Swap）

* 示例：**将 BNB Chain 上的 BNB 兑换为 Arbitrum 上的 ARB**
* 将 BNB 兑换为桥接代币（使用户产出最大化）
* 通过 Across 桥接
* 使用 Arbitrum 上的 PancakeSwap 池将桥接后的代币兑换为 ARB

***

### ⚠️ 失败情形

| 情形              | 结果                                                                               |
| --------------- | -------------------------------------------------------------------------------- |
| **源链上的兑换/交易失败** | 用户立即在源链上收到原始代币                                                                   |
| **桥接交易失败**      | Across 会在 90 分钟到 2 小时内处理退款，用户在源链上收到桥接资产。而在 SOL <> EVM 之间的此类情形下，Relay 会在一分钟内处理退款。 |
| **目标链上的兑换失败**   | 用户在目标链上收到桥接资产                                                                    |


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